Titration is the process of measuring the concentration of a strong acid in a water solution by using an indicator and adding a base to neutralize it. As stated before, neutralization reactions result in a salt and water being produced. After titration, when a point of equality is reached, there are equal moles, equal volumes, and equal molarities of the acid and the base. Get this: if you really know what you're doing, you can completely neutralize an acid with a base (or vice versa) and get a solution safe enough to drink. Granted, no one would recommend you try that at home, or even in a chemistry classroom.
If the molarity of the acid or the base is known, the molarity of the other can be found. It's crucial to find out the concentration of H+ ions and know that that number is equal to the concentration of OH- ions. Those numbers can then be divided by the volume (in L) of the substance with the unknown molarity. (If that doesn't make much sense, see the problems below)
Problems:
3.) How many mL of 0.1 M NaOH would be needed to neutralize 2.0 L of 0.050 M HCl?
First, know that 2.0 L = 2,000 mL.
0.050 M / 2,000 mL = 0.1 M / x mL
0.050 M( x mL) = 0.050x
2,000 mL( 0.1 M) = 200
200 / 0.050 = 4,000 mL
It would take 4,000 mL of NaOH to neutralize the HCl.
Another way to look at this is to realize that the molarity of the HCl is 1/2 the molarity of the NaOH solution. This means you can convert the HCl volume into mL (2,000 mL) and multiply that by 2 to get 4,000 mL.
5.) A student mixes 100 mL of 0.20 M HCl with different volumes of 0.50 M NaOH. Are these final solutions acidic, basic, or neutral?
a.) 100 mL of 0.20 M HCl + 20 mL of 0.50 M NaOH Acidic (because there's more of the solution with the lower molarity and that overpowers the base)
b.) 100 mL of 0.20 M HCL + 40 mL of 0.50 M NaOH Neutral (there is enough base to neutralize the acid, despite their different molarities)
c.) 100 mL of 0.20 M HCl + 60 mL of 0.50 M NaOH Basic (if 40 is the neutral point, anything above that as far as the NaOH is concerned should be basic.)
Friday, November 30, 2012
Thursday, November 29, 2012
Unit 4, Lesson 21
A neutralization reaction, also considered a double exchange reaction, occurs when a base is used to render an acid neutral, or when an acid is used to neutralize a base. When an acid and base are mixed, an aqueous, ionic compound (a salt) and H2O (water) are produced. In pure water kept at 25 degrees C, when there are equal amounts of acid and base, there are equal amounts of H+ ions and OH- ions.
There are weak acids and bases, and strong acids and bases. Strong acids and bases dissociate (break apart) completely in water and completely disperse their ions. They are also the most dangerous acids and bases and don't mean good news when they come into contact with skin, your insides, your clothing, etc. Weak acids and bases, however, do not dissociate completely. They're generally safer. Some typical weak acids are vinegar and citric acid, which is found in fruit. Ammonia, a household cleaner, is a weak base (but, like any kind of soap or cleaner, shouldn't be ingested. Not that smart Chem Honors kids need to be reminded of that!)
Problems:
5.) Suppose you mix 1 mol of sulfuric acid, H2SO4, with 1 mol of sodium hydroxide, NaOH. Why does the pH of the solution remain below 7? There are not enough H+ ions in NaOH to neutralize the H+ ions in the sulfuric acid, which has 2 hydrogen. There are also not enough oxygen atoms. Either you need more sodium hydroxide, or a stronger base to neutralize the H2SO4.
8.) What combination of reactants would result in a neutralization reaction with sodium nitrate, NaNO3, as one of the products? (Mg(NO3)2 + NaOH, HNO3 + NaOH, CH3OH + NaOH, HNO3 + NaCl) Combination D, which is HNO3 + NaCl.
There are weak acids and bases, and strong acids and bases. Strong acids and bases dissociate (break apart) completely in water and completely disperse their ions. They are also the most dangerous acids and bases and don't mean good news when they come into contact with skin, your insides, your clothing, etc. Weak acids and bases, however, do not dissociate completely. They're generally safer. Some typical weak acids are vinegar and citric acid, which is found in fruit. Ammonia, a household cleaner, is a weak base (but, like any kind of soap or cleaner, shouldn't be ingested. Not that smart Chem Honors kids need to be reminded of that!)
Problems:
5.) Suppose you mix 1 mol of sulfuric acid, H2SO4, with 1 mol of sodium hydroxide, NaOH. Why does the pH of the solution remain below 7? There are not enough H+ ions in NaOH to neutralize the H+ ions in the sulfuric acid, which has 2 hydrogen. There are also not enough oxygen atoms. Either you need more sodium hydroxide, or a stronger base to neutralize the H2SO4.
8.) What combination of reactants would result in a neutralization reaction with sodium nitrate, NaNO3, as one of the products? (Mg(NO3)2 + NaOH, HNO3 + NaOH, CH3OH + NaOH, HNO3 + NaCl) Combination D, which is HNO3 + NaCl.
Unit 4, Lesson 20
The process of "watering down" an acidic or basic solution is called dilution. It simply entails adding water to an acid or base to, in an acid's case, raise the pH toward 7, or in a base's case, lower the pH toward 7. 7 is considered "neutral" for any substance. Diluting a substance makes it weaker, or less concentrated, since adding water lowers the molarity. When the molarity of an acid or base is lowered, the pH increases by 1. This is because the pH scale is logarithmic, and a tiny change in pH makes for a huge change in concentration. For example, changing an acid from a pH of 3 to a pH of 4 makes that acid 10x less acidic. Changing it to pH 5 is 100x more acidic. pH 6, 1000x more acidic, and so on.
Though diluting an acid or base is meant to make it more neutral, one cannot achieve full neutrality. Rather, they can get very close. An acid can only be diluted to a pH between 6 and 6.9. A base can only be diluted to a pH around 7.1 (or 8, because any pH above 7 is basic).
Problems:
2.) Explain why you can't turn an acid into a base by diluting with water. You can't eliminate the acid completely--you can only neutralize it, because water is neutral. However, if you were diluting with a base, you could change the acid, because the pH would gradually raise until it was high enough to be a base.
4.) How much water do you need to add to 10 mL of a solution of HCl with a pH of 3 to change it to a pH of 6? 999 mL of water.
pH of 3 = .0010 M
pH of 4 = .00010 M (10x less acidic) (+9 mL of water)
pH of 5 = .000010 M (100x less acidic) (+99 mL of water)
pH of 6 = .0000010M (1,000x less acidic) (+999 mL of water)
...I don't know if that's correct. I'm a bit fuzzy on this myself.
Though diluting an acid or base is meant to make it more neutral, one cannot achieve full neutrality. Rather, they can get very close. An acid can only be diluted to a pH between 6 and 6.9. A base can only be diluted to a pH around 7.1 (or 8, because any pH above 7 is basic).
Problems:
2.) Explain why you can't turn an acid into a base by diluting with water. You can't eliminate the acid completely--you can only neutralize it, because water is neutral. However, if you were diluting with a base, you could change the acid, because the pH would gradually raise until it was high enough to be a base.
4.) How much water do you need to add to 10 mL of a solution of HCl with a pH of 3 to change it to a pH of 6? 999 mL of water.
pH of 3 = .0010 M
pH of 4 = .00010 M (10x less acidic) (+9 mL of water)
pH of 5 = .000010 M (100x less acidic) (+99 mL of water)
pH of 6 = .0000010M (1,000x less acidic) (+999 mL of water)
...I don't know if that's correct. I'm a bit fuzzy on this myself.
Sunday, November 25, 2012
Disappearing Spoon- Ch. 8-9
Chapter 8:
Attention to detail plays a humongous role in science. Making sure you have the correct information in an experiment, or while researching, prevents you from having to deal with a bunch of skewed data in the end. Unfortunately, the scientists Pauling and Segre didn't quite grasp this concept. In a feverish race to catch a Nobel Prize, they were doing research in their own fields and working together at Berkeley. Pauling was studying DNA and its ability to carry genetic information. He made a big mistake and observed a dry sample of DNA rather than a wet one. The two had different numbers of helixes, and in studying the dry one, he missed out on his shot at the Nobel Prize. Some students at Cambridge discovered Pauling's mistake and claimed the prize for their own. Segre was among the many who wanted to discover new elements. He took to experimenting with strips of molybdenum, hoping to find some element hidden inside of it. He did: technetium. Technetium is element 43, and was perhaps the most elusive of all the elements in the table. Several claimed they'd discovered it for the "first time", only to be proved wrong.
Chapter 9:
This chapter discussed toxic elements that are present in our everyday lives, and how they can harm us. Sometimes we don't even realize that radioactive, unstable, and in other ways toxic elements are around us. One such element is cadmium. Cadmium was a product of warfare, specifically Japanese warfare. After the battles had been fought, remnants of the toxic element could be found in the water. There were some rice farmers near the Kamioka mines that ate what they harvested and fell sick with mysterious illnesses. These illnesses seemed to be chronic, and it was discovered later that cadmium is toxic when ingested. In spite of this, cadmium is not the most poisonous element--no, those are lead, thallium, and polonium. There are other elements, like the alkali metals, that would literally explode inside someone once they came into contact with any moisture. Chapter 9 also talked about how troublesome kids can be when they get their heads into science. David Hahn, described by Kean as a sixteen year old boy scout, spent a lot of time in his mother's shed playing with something crude. Something he called a nuclear reactor. It was his wish to end the world's hunger for oil by offering them an alternative. His young research didn't go very far; he got stuck doing chore-like work.
Attention to detail plays a humongous role in science. Making sure you have the correct information in an experiment, or while researching, prevents you from having to deal with a bunch of skewed data in the end. Unfortunately, the scientists Pauling and Segre didn't quite grasp this concept. In a feverish race to catch a Nobel Prize, they were doing research in their own fields and working together at Berkeley. Pauling was studying DNA and its ability to carry genetic information. He made a big mistake and observed a dry sample of DNA rather than a wet one. The two had different numbers of helixes, and in studying the dry one, he missed out on his shot at the Nobel Prize. Some students at Cambridge discovered Pauling's mistake and claimed the prize for their own. Segre was among the many who wanted to discover new elements. He took to experimenting with strips of molybdenum, hoping to find some element hidden inside of it. He did: technetium. Technetium is element 43, and was perhaps the most elusive of all the elements in the table. Several claimed they'd discovered it for the "first time", only to be proved wrong.
Chapter 9:
This chapter discussed toxic elements that are present in our everyday lives, and how they can harm us. Sometimes we don't even realize that radioactive, unstable, and in other ways toxic elements are around us. One such element is cadmium. Cadmium was a product of warfare, specifically Japanese warfare. After the battles had been fought, remnants of the toxic element could be found in the water. There were some rice farmers near the Kamioka mines that ate what they harvested and fell sick with mysterious illnesses. These illnesses seemed to be chronic, and it was discovered later that cadmium is toxic when ingested. In spite of this, cadmium is not the most poisonous element--no, those are lead, thallium, and polonium. There are other elements, like the alkali metals, that would literally explode inside someone once they came into contact with any moisture. Chapter 9 also talked about how troublesome kids can be when they get their heads into science. David Hahn, described by Kean as a sixteen year old boy scout, spent a lot of time in his mother's shed playing with something crude. Something he called a nuclear reactor. It was his wish to end the world's hunger for oil by offering them an alternative. His young research didn't go very far; he got stuck doing chore-like work.
Thursday, November 15, 2012
Unit 4, Lesson 19
Suppose you have a solution whose pH you know, but whose concentration of H+ ions and OH- ions you don't know. There's a simple formula you can use to find any of your missing links, and it is as follows:
pH = -log[ H+]
[ H+] = 10^-pH
The first equation is used to find the pH of the substance if the number of hydrogen ions (which is listed in scientific notation) is known. The second, scientists use to find hydrogen ions by taking the pH, making it a negative number, and writing it in scientific notation.
To find OH- ions, know that the product of hydrogen and hydroxide ions is always equivalent to 1 x 10^-14. If you know one value of ions, divide 1 x 10^-14 by it to find the other value.
Problems:
7.) What is the pH of a 2.5 M HCl solution? The pH of this solution is 0, because the decimal is after the 2, not before. Its H+ concentration is 1 x 10^0.
8.) What is the pH of a 0.256 M NaOH solution? 11. The H+ concentration is 1 x 10^-11, the OH- concentration is 1 x 10^-3.
Unit 4, Lessons 17 and 18
Lesson 17:
Substances can be classified as acids, bases, or neutral solutions. Whether or not a solution gets classified as one of those three depends on its pH, which is a measure of the concentration of hydrogen and hydroxide ions. Acids have a very low pH number (anything less than 7). Bases sit on the complete other side of the scale and have pHs above 7. Any solution with a pH of exactly 7 is neutral. Table salt and pure water are neutral; lemon juice is an acid (FUN FACT: so is milk!), and soap is a base. Acids and bases are both very corrosive and sometimes unsafe to handle. How exactly does one tell if a solution is acidic or basic? Through the use of an indicator, a molecular substance that changes colors in acidic and basic environments. There are two common types of indicators: cabbage juice (easily accessible at home) and Universal Indicator (not as easily acquired, but much more accurate).
Problems:
1.) What are some observable properties of acids and bases? Acids are typically sour, if they're safe to eat. Bases, like soap, taste bitter and sometimes foam up in water. Both acids and bases can be corrosive.
2.) What is the pH scale? The pH scale is a colored number line, essentially, that associates different types of solutions with colors to help one determine if they're basic or acidic. Basic solutions are usually in darker greens, blues, and purples on the scale; acids show up as vibrant reds, oranges, and yellows.
Lesson 18:
The laws for identifying basic, neutral, and acidic solutions have changed over time. Most of the laws, though, have always involved the hydrogen and hydroxide ions that pH measures. In a chemical reaction, acids give away one H+ ion, which shows up in the products. The product that has one more H+ ion than before is the starting acid (reactant)'s corresponding base. Oppositely, bases give off OH- ions in their reactions, and the product that receives the base's OH- is its corresponding acid. In these processes, which are defined Arrheniously, Bronsted-Lowry's law comes into play. It states that acidic solutions are proton donors (since H+ ions are simply stray protons) and basic solutions are proton acceptors.
Problems:
2.) How is the Bronsted-Lowry theory of acids similar to the Arrhenius theory? How is it different? These two theories are similar in that they both deal with the identification of solutions as acids/bases through whatever ions are present. They're different in that the Arrhenius theory doesn't explain how solutions without OH- ions in their chemical formulas can be bases, too.
7.) Explain why aqueous washing soda, NaCO3, is a basic solution. It is a basic solution because it has one OH- ion in its composition. (Also, it's a kind of soap, which is also a giveaway).
Substances can be classified as acids, bases, or neutral solutions. Whether or not a solution gets classified as one of those three depends on its pH, which is a measure of the concentration of hydrogen and hydroxide ions. Acids have a very low pH number (anything less than 7). Bases sit on the complete other side of the scale and have pHs above 7. Any solution with a pH of exactly 7 is neutral. Table salt and pure water are neutral; lemon juice is an acid (FUN FACT: so is milk!), and soap is a base. Acids and bases are both very corrosive and sometimes unsafe to handle. How exactly does one tell if a solution is acidic or basic? Through the use of an indicator, a molecular substance that changes colors in acidic and basic environments. There are two common types of indicators: cabbage juice (easily accessible at home) and Universal Indicator (not as easily acquired, but much more accurate).
Problems:
1.) What are some observable properties of acids and bases? Acids are typically sour, if they're safe to eat. Bases, like soap, taste bitter and sometimes foam up in water. Both acids and bases can be corrosive.
2.) What is the pH scale? The pH scale is a colored number line, essentially, that associates different types of solutions with colors to help one determine if they're basic or acidic. Basic solutions are usually in darker greens, blues, and purples on the scale; acids show up as vibrant reds, oranges, and yellows.
Lesson 18:
The laws for identifying basic, neutral, and acidic solutions have changed over time. Most of the laws, though, have always involved the hydrogen and hydroxide ions that pH measures. In a chemical reaction, acids give away one H+ ion, which shows up in the products. The product that has one more H+ ion than before is the starting acid (reactant)'s corresponding base. Oppositely, bases give off OH- ions in their reactions, and the product that receives the base's OH- is its corresponding acid. In these processes, which are defined Arrheniously, Bronsted-Lowry's law comes into play. It states that acidic solutions are proton donors (since H+ ions are simply stray protons) and basic solutions are proton acceptors.
Problems:
2.) How is the Bronsted-Lowry theory of acids similar to the Arrhenius theory? How is it different? These two theories are similar in that they both deal with the identification of solutions as acids/bases through whatever ions are present. They're different in that the Arrhenius theory doesn't explain how solutions without OH- ions in their chemical formulas can be bases, too.
7.) Explain why aqueous washing soda, NaCO3, is a basic solution. It is a basic solution because it has one OH- ion in its composition. (Also, it's a kind of soap, which is also a giveaway).
Monday, November 12, 2012
Disappearing Spoon, Ch. 5-7
Chapter five taught me that The Disappearing Spoon is an excellent choice of reading material for long car rides between states. Kean talked at length about Fritz Haber and his ground-breaking chemical contributions to German warfare. I found myself a bit resentful toward Haber when I read how he treated his wife and his friends. I suppose that it really is possible to devote every speck of your soul to science. Fritz's specialty when tinkering with his chemicals was creating deadly gas weapons that could wipe out entire armies of enemy men. His formulas were potent, containing elements of chlorine, bromine, and nitrogen. Ironically, this man of scientific genius got what was coming to him in throwing away his personal relationships. He ended up being captured for being Jewish by Nazis, and a watered-down version of one of his gases was used in concentration camps to eradicate other Jews. Right in the feel-bads, huh? I have to say, one of my favorite elements of this book so far is the heavy amount of German history in it.
In chapter six, the material focused on how the last few spots in Mendeleev's periodic table were filled. It's tragic to look at dear promethium, with its dark and mysterious name, and know that it wasn't good for much but taking a seat among other relatively useless elements. As I (and Kean) mentioned before, Mendeleev's table underwent tons of changes after the time of its creation. Everything from rearranging the order of Mendeleev's elements, to changing the degree at which the table sits, happened. A man named Henry Moseley helped sort out some crucial kinks in the table, like switching elements that didn't make sense. He was the one to propose that elements should be placed in order of increasing atomic number, along with mass. After Moseley joined the army and was killed in action, a sequence of finding new elements for the table began, and after that, the neutron was discovered and used to explain isotopes. Scientists and the public now understood that two elements could have different weights, but still keep their identity, which kept some people from throwing elements out of the table. The rest of the chapter sort of went on about the Manhattan Project and the team's unorthodox experimentation. Kean's tone seemed interested (as it always has, up to this point) in the method of throwing random numbers into a sequence, calculating, and hoping a good product would emerge. This kind of testing, I realized, is sort of like the scientific method that we're taught today: observe, hypothesize, conduct the experiment. If something doesn't turn out right, change a variable and do it all again.
In chapter seven, Kean frantically went on about Berkeley and its feverish endeavor to find as many elements for the table as possible. Of course, they couldn't have all the elements out there to themselves, so other countries outside the U.S., like Russia, were quick to try their hand at the synthesizing process. When someone other than Berkeley came up with a new element, the lab checked their work. They didn't take kindly to seeing correct data different than theirs. (Like a kid who thinks they always have to be right!) Naming elements proved, challenging, too, because some names were either dry or offensive to the public. Believe it or not, communism in Russia affected the scientists that were trying to fill the table. Joseph Stalin and his followers were among perhaps the most stubborn of men and didn't believe that what the scientists were trying was legitimate. He thought it traitorous to his socialist government and tried to have the process shut down, executing physicists and chemists alike or forcing them to work in unimaginable conditions. So many people tried to get in on naming/synthesizing new elements that the endeavor became more of a game than a race to fill the table, and when people started fighting over who could earn a square on the periodic table, a high-and-mighty, official team of people had to sift through all the B.S. and decide.
Friday, November 9, 2012
Unit 4, Lessons 15 and 16
Lesson 15:
One can create a solution with a specific molarity by using the molar mass of the solid. If the amount of solid you have is given, you can find out how many moles of that substance are needed with a chart (which we've already gone over) and the molar mass. If the concentration or the volume is given, you can substitute it into the molarity concentration to find the other value you need. For example, if you need .01 L of a 0.5 M solution, you would need 0.5 grams of your solute. How did I get this? Plug the known values into the molarity equation to get 0.5 = n / 0.01. Multiply each side by 0.01 to get n = 0.005 moles of solute. Convert moles to grams of solute by using the molar mass of, in this case, NaBr, to get 0.515 g. That rounds to 0.5!
Problems:
1.) Explain how you would create a solution of sucrose with a molarity of 0.25. I think I would first need to know the volume of solution I am making. Then, I would multiply that volume by the molarity, 0.25 M, to get my # of moles. I would convert the moles to grams and that would tell me how much sucrose I need to make this solution.
6.) How many grams of fructose, C6H12O6, are in 1 L of soft drink if the molarity of fructose in the drink is 0.75 M? First off, the molar mass of fructose is about 180 g. In the equation 0.75 M = n / 1, I find that this solution has 0.75 moles of fructose. Converting moles to grams, I multiply 0.75 by 180 and get 135 grams of fructose in this soft drink.
Lesson 16:
We really didn't have many notes for this lesson, since we really just perfected our skills from 15. The gist of lesson 16 is that the type of substance being dissolved in a solution affects the whole solution's mass. The mass of one mole of one substance could be very different than the mass of one mole of another substance.
Problems:
1.) Explain how you might use mass to determine if a sample of water is contaminated. You might be able to figure out if the water is contaminated by finding its density/mass and then comparing the sample to a sample of "normal" water. If the results are different, one sample of water probably has some extra substances in it, like minerals or toxins.
3.) Explain why 0.10 M CuCl2 has a greater density than 0.10 M KCl. The densities are different because the solutions contain two different compounds, and CuCl2 has a greater molar mass than KCl.
One can create a solution with a specific molarity by using the molar mass of the solid. If the amount of solid you have is given, you can find out how many moles of that substance are needed with a chart (which we've already gone over) and the molar mass. If the concentration or the volume is given, you can substitute it into the molarity concentration to find the other value you need. For example, if you need .01 L of a 0.5 M solution, you would need 0.5 grams of your solute. How did I get this? Plug the known values into the molarity equation to get 0.5 = n / 0.01. Multiply each side by 0.01 to get n = 0.005 moles of solute. Convert moles to grams of solute by using the molar mass of, in this case, NaBr, to get 0.515 g. That rounds to 0.5!
Problems:
1.) Explain how you would create a solution of sucrose with a molarity of 0.25. I think I would first need to know the volume of solution I am making. Then, I would multiply that volume by the molarity, 0.25 M, to get my # of moles. I would convert the moles to grams and that would tell me how much sucrose I need to make this solution.
6.) How many grams of fructose, C6H12O6, are in 1 L of soft drink if the molarity of fructose in the drink is 0.75 M? First off, the molar mass of fructose is about 180 g. In the equation 0.75 M = n / 1, I find that this solution has 0.75 moles of fructose. Converting moles to grams, I multiply 0.75 by 180 and get 135 grams of fructose in this soft drink.
Lesson 16:
We really didn't have many notes for this lesson, since we really just perfected our skills from 15. The gist of lesson 16 is that the type of substance being dissolved in a solution affects the whole solution's mass. The mass of one mole of one substance could be very different than the mass of one mole of another substance.
Problems:
1.) Explain how you might use mass to determine if a sample of water is contaminated. You might be able to figure out if the water is contaminated by finding its density/mass and then comparing the sample to a sample of "normal" water. If the results are different, one sample of water probably has some extra substances in it, like minerals or toxins.
3.) Explain why 0.10 M CuCl2 has a greater density than 0.10 M KCl. The densities are different because the solutions contain two different compounds, and CuCl2 has a greater molar mass than KCl.
Unit 4, Lessons 13 and 14
Lesson 13:
A solution is a mixture of two or more substances that is uniform throughout. You can keep track of what you're putting into a solution by measuring the number of particles. That said, we call the total number of particles the concentration of the solution, which is simply how densely saturated a solution is with something. (Example: how much hot chocolate powder is in a mug of hot water. More powder= higher concentration, more chocolateness. Less powder = lower concentration, less chocolateness. Ew.) Another, more science-y word for concentration is molarity, represented by the following equation:
A solution is a mixture of two or more substances that is uniform throughout. You can keep track of what you're putting into a solution by measuring the number of particles. That said, we call the total number of particles the concentration of the solution, which is simply how densely saturated a solution is with something. (Example: how much hot chocolate powder is in a mug of hot water. More powder= higher concentration, more chocolateness. Less powder = lower concentration, less chocolateness. Ew.) Another, more science-y word for concentration is molarity, represented by the following equation:
Molarity (M) = number of moles (n) / Volume (L)
Problems:
1.) What does it mean when a solution is "uniform throughout"? This means that the solute. Has been thoroughly dissolved in a solvent and there are no random particles or "floaties" in the liquid.
5.) Put these three solutions in order of increasing molarity.
A.) 4.0 mol per 8.0 L: molarity is 0.5 mol/L
B.) 6.0 mol per 6.0 L: molarity is 1 mol/L
C.) 1.0 mol per10 L: molarity is 0.1 mol/L
Order: C, A, B.
1.) What does it mean when a solution is "uniform throughout"? This means that the solute. Has been thoroughly dissolved in a solvent and there are no random particles or "floaties" in the liquid.
5.) Put these three solutions in order of increasing molarity.
A.) 4.0 mol per 8.0 L: molarity is 0.5 mol/L
B.) 6.0 mol per 6.0 L: molarity is 1 mol/L
C.) 1.0 mol per10 L: molarity is 0.1 mol/L
Order: C, A, B.
Lesson 14:
In this lesson, we learned the relation of concentration to volume. The concentration does not change if the volume of the solution changes. If a solute is dissolved thoroughly and evenly in the solvent, the number of particles, or the molarity, should not change. Because of this, the equation mentioned in lesson 13 can be used to find molarity, volumes, and the moles in just about any solution.
Problems:
2.) How can you figure out how many moles of solute you have in a solution with a specific concentration? In the equation molarity = moles / volume, finding the number of moles requires multiplying both sides by the volume.
5.) Glucose and sucrose are two different types of sugar. Consider these aqueous solutions: 1.0 L of 1.0 M C6H12O6 (glucose), 1.0 L of 1.0 M C12H22O11 (sucrose), 500mL of 1.0 M C12H22O11 (sucrose):
A.) Which solution has the most molecules? Explain. The glucose solution, because it has the lowest molar mass for the given volume of solvent.
B.) Which solution is most concentrated? Explain. The glucose solution, because it has more molecules for a given volume and is more saturated with glucose.
C.) Which solution has the most mass? Explain. The first sucrose solution has the most mass, because it has a larger volume than the last sucrose solution and sucrose has a larger molar mass than glucose.
Problems:
2.) How can you figure out how many moles of solute you have in a solution with a specific concentration? In the equation molarity = moles / volume, finding the number of moles requires multiplying both sides by the volume.
5.) Glucose and sucrose are two different types of sugar. Consider these aqueous solutions: 1.0 L of 1.0 M C6H12O6 (glucose), 1.0 L of 1.0 M C12H22O11 (sucrose), 500mL of 1.0 M C12H22O11 (sucrose):
A.) Which solution has the most molecules? Explain. The glucose solution, because it has the lowest molar mass for the given volume of solvent.
B.) Which solution is most concentrated? Explain. The glucose solution, because it has more molecules for a given volume and is more saturated with glucose.
C.) Which solution has the most mass? Explain. The first sucrose solution has the most mass, because it has a larger volume than the last sucrose solution and sucrose has a larger molar mass than glucose.
Sunday, November 4, 2012
Disappearing Spoon, Ch.3-4
Reading about a man who toiled with arsenic is, to say the least, a bit disturbing. Arsenic has an explosive love-hate relationship with just about anything, it seems, even Robert Bunsen. As anyone well knows, arsenic is deadly stuff. Robert Bunsen loved messing with elements and, like most chemists would be, enjoyed finding new ones. He invented the first spectroscope a tool that identifies unknown substances by color. It resembles a cowbell, almost. A page or two into the chapter, Kean switches gears and starts talking about the periodic table again, this time disputing who made it. Great minds think alike, and when Mendeleev first began piecing together the structure that we know today, many others were doing the same. Mendeleev is given credit for the periodic table even though he did not discover all the elements needed to complete it, like the lanthanides.
In chapter 4, a reader learns just how silly humanity can be. That might seem cynical, but the reality that humans like to make [expletive] up is quite comical. When sticking their heads together to try and find out where elements hailed from, or if they could be forged, some pretty ridiculous theories arose. A giant comet landing on Earth and wiping out the dinosaurs was proposed as an explanation, most likely for the amount of heat and energy that resulted upon impact. Since those phenomena happen patterns an ungodly amount of years apart, it's possible that new elements could result from whatever comes to destroy the human race. Perhaps UFOs could give us our next set of tinker toys! Most know that elements like gold can only be forged in celestial explosions, a.k.a. supernovas, and don't appear on earth by human means. Supernovas are logically the producers of other elements, just like we're starchildren made of cosmic dust.
In chapter 4, a reader learns just how silly humanity can be. That might seem cynical, but the reality that humans like to make [expletive] up is quite comical. When sticking their heads together to try and find out where elements hailed from, or if they could be forged, some pretty ridiculous theories arose. A giant comet landing on Earth and wiping out the dinosaurs was proposed as an explanation, most likely for the amount of heat and energy that resulted upon impact. Since those phenomena happen patterns an ungodly amount of years apart, it's possible that new elements could result from whatever comes to destroy the human race. Perhaps UFOs could give us our next set of tinker toys! Most know that elements like gold can only be forged in celestial explosions, a.k.a. supernovas, and don't appear on earth by human means. Supernovas are logically the producers of other elements, just like we're starchildren made of cosmic dust.
Disappearing Spoon: Intro, Ch.1-2
The Disappearing Spoon begins by likening the periodic table to some kind of ancient treasure. A holy grail of ordinary people and scientists. Though Sam Kean chooses to focus on the element mercury throughout the introduction, he always ties his points back to a central idea, that the periodic table stands as the basic building block, as atoms do, for all scientific play. He begins his story by retelling for the reader a childhood memory of catching strep throat and having his mouth full of mercury thermometers. Living in an age where it appears taboo to handle the stuff, I was eager to read about his early experiences with mercury. By describing the silvery metal as though it's living, breathing, and existing as humans do, Kean creates an atmosphere that clearly lays out the importance--and interest--of the periodic table.
Like fat and happy kings on thrones, the elements live in a castle called the periodic table. The only reference to this analogy is in the beginning of chapter 1 (which, might I add, was painfully tedious to read). While Kean doesn't go too in depth in explaining why the elements situate themselves how they do, he does describe how the castle would crumble if one was removed from its spot. The chapter talks about the properties of each part of the periodic table, like how alkali metals react easily and quickly with halogens. Kean throws in some nifty scientific history, sarcastically spinning the tales of under-appreciated chemists from Germany.
If ever someone has tried to read a really long word and gotten discouraged enough to shut the book, it happened in chapter two, with the tongue-twister that is the tobacco mosaic virus. Its word is just that--a mosaic. For only the most artful of tongues. Kean seems flirtatious with carbon in this chapter, diving into its properties in forming amino acids. He takes a breath and tells the reader what an amino acid is, as well. (This book might as well be a Chemistry lesson; Darcy, I can see where you found it dry.) The chapter ends with a sweet little description of silicon and germanium integration in technology.
Like fat and happy kings on thrones, the elements live in a castle called the periodic table. The only reference to this analogy is in the beginning of chapter 1 (which, might I add, was painfully tedious to read). While Kean doesn't go too in depth in explaining why the elements situate themselves how they do, he does describe how the castle would crumble if one was removed from its spot. The chapter talks about the properties of each part of the periodic table, like how alkali metals react easily and quickly with halogens. Kean throws in some nifty scientific history, sarcastically spinning the tales of under-appreciated chemists from Germany.
If ever someone has tried to read a really long word and gotten discouraged enough to shut the book, it happened in chapter two, with the tongue-twister that is the tobacco mosaic virus. Its word is just that--a mosaic. For only the most artful of tongues. Kean seems flirtatious with carbon in this chapter, diving into its properties in forming amino acids. He takes a breath and tells the reader what an amino acid is, as well. (This book might as well be a Chemistry lesson; Darcy, I can see where you found it dry.) The chapter ends with a sweet little description of silicon and germanium integration in technology.
Thursday, November 1, 2012
Unit 4, Lessons 11 and 12
Lesson 11:
Like I've already touched on, you can find out how many moles of molecules are in a sample or how many grams that sample weighs by the use of these two tables:
x moles (sample) | y grams
---------------------------------------------------- = # of grams
| 1 mole (molar mass)
Sometimes, the unit isn't grams, but milligrams, or perhaps micrograms. Some simple conversions can help with that inconvenience. For example, 1000 milligrams = 1 gram. It's very important to have all your masses in the same units before you try to find moles or grams.
Problems:
2.) Why might a 200 mg tablet of aspirin not have the same effect as a 200 mg tablet of ibuprofen? They are two different medications and their dosages may be different depending on how old the person taking the medication is.
5.) Which has more moles of oxygen atoms, 153 g of BaO or 169 g of BaO2? BaO2 has more moles of oxygen atoms because the number of moles is always equivalent to the value of the subscript. Since there are two atoms of oxygen in BaO2 vs. only one atom in BaO, BaO2 has two moles of oxygen.
Lesson 12:
This lesson talked about how the LD50 doesn't take into consideration the long-term effects of certain toxins. If a substance's molar mass is large, it takes less of that substance to achieve a lethal does. If it has a small mass, it takes more of it. Even if it takes less to poison one with a substance, it doesn't necessarily negate the fact that there can be pretty nasty side effects. For example, an easily-achieved overdose, if it fails, can leave one with severe liver damage, ulcers, and perhaps even neurological damage.
Problems:
2.) What evidence shows that it would be difficult to exceed the lethal dose of aspartame? The LD50 for aspartame is 10 g/kg. Depending on how much aspartame is used in a can of soda, or any other artificially-sweetened drink, it takes a long time to drink a ton of diet soda. You will not achieve a lethal dose of aspartame in a short time.
4.) The LD50 for saccharin, C7H5NO3S, is 14.2 g/kg. If you have 1 mole of aspartame and 1 mole of saccharin, which would be more toxic? Show your work. The LD50 for aspartame is 10g/kg, which is less than the LD50 for saccharin. It's easy to look at those two numbers and decide that aspartame is the more toxic of the two, because it takes less of it to both sweeten a drink, or poison someone.
Like I've already touched on, you can find out how many moles of molecules are in a sample or how many grams that sample weighs by the use of these two tables:
x grams (sample) | 1 mole
------------------------------------------------------ = # of moles
| y grams (molar mass)
---------------------------------------------------- = # of grams
| 1 mole (molar mass)
Sometimes, the unit isn't grams, but milligrams, or perhaps micrograms. Some simple conversions can help with that inconvenience. For example, 1000 milligrams = 1 gram. It's very important to have all your masses in the same units before you try to find moles or grams.
Problems:
2.) Why might a 200 mg tablet of aspirin not have the same effect as a 200 mg tablet of ibuprofen? They are two different medications and their dosages may be different depending on how old the person taking the medication is.
5.) Which has more moles of oxygen atoms, 153 g of BaO or 169 g of BaO2? BaO2 has more moles of oxygen atoms because the number of moles is always equivalent to the value of the subscript. Since there are two atoms of oxygen in BaO2 vs. only one atom in BaO, BaO2 has two moles of oxygen.
Lesson 12:
This lesson talked about how the LD50 doesn't take into consideration the long-term effects of certain toxins. If a substance's molar mass is large, it takes less of that substance to achieve a lethal does. If it has a small mass, it takes more of it. Even if it takes less to poison one with a substance, it doesn't necessarily negate the fact that there can be pretty nasty side effects. For example, an easily-achieved overdose, if it fails, can leave one with severe liver damage, ulcers, and perhaps even neurological damage.
Problems:
2.) What evidence shows that it would be difficult to exceed the lethal dose of aspartame? The LD50 for aspartame is 10 g/kg. Depending on how much aspartame is used in a can of soda, or any other artificially-sweetened drink, it takes a long time to drink a ton of diet soda. You will not achieve a lethal dose of aspartame in a short time.
4.) The LD50 for saccharin, C7H5NO3S, is 14.2 g/kg. If you have 1 mole of aspartame and 1 mole of saccharin, which would be more toxic? Show your work. The LD50 for aspartame is 10g/kg, which is less than the LD50 for saccharin. It's easy to look at those two numbers and decide that aspartame is the more toxic of the two, because it takes less of it to both sweeten a drink, or poison someone.
Unit 4, Lessons 9 and 10
Lesson 9:
Scientists use scientific notation to express numbers that are very big or very small. Correct scientific notation has only 1 digit before the decimal point! We've studied the use of scientific notation to express how many molecules are in a test sample. Once again, we looked at moles. One mole, 602 sextillion, is written in scientific notation as 6.022 x 10^23. The term "molar mass" refers to how much of a substance is needed to achieve 1 mole of molecules. The molar masses for all the known elements are the same as the atomic masses on the periodic table. Molar mass helps scientists convert between moles of atoms and grams of atoms. That's where the two tables I mentioned in lesson 7 come into play.
Problems:
4.) Give the molar mass for these elements:
A.) nitrogen, N - 14.0 g
B.) neon, Ne - 20.2 g
C.) chlorine, Cl - 35.5 g
D.) copper, Cu - 63.5 g
6.) Which contains more atoms?
A.) 12 g of hydrogen, H, or 12 g of carbon, C? 12 g of hydrogen. Hydrogen has the smaller molar mass.
B.) 27 g of aluminum, Al, or 27 g of iron, Fe? 27 g of aluminum. Aluminum has the smaller molar mass.
C.) 40 g of calcium, Ca, or 40 g of sodium, Na? 40 g of sodium. Sodium has the smaller molar mass.
D.) 40 g of calcium, Ca, or 40 g of zinc, Zn? 40 g of calcium. Calcium has the smaller molar mass.
E.) 10 g of lithium, Li, or 100 g of lead, Pb? 100 g of Pb, because it has the larger sample size.
Lesson 10:
Because individual atoms cannot be counted easily by themselves, scientists compare moles of substances rather than masses of substances. If one was given 50 moles of one element and 50 moles of another, their molar masses are significant, but only in telling which element would be lighter. Then, it's up to us to decide which sample is larger based off of how many more/less atoms it takes to make an equal sample. If given a compound, where the molar mass isn't clear but rather a bunch of molar masses thrown together, one must add the masses of each element in the compound, multiply by the subscripts (if there are any) and add all the masses together to find the compound's whole mass.
Problems:
5.) Which has more moles of metal atoms?
A.) 10.0 g of calcium, Ca, or 10.0 g of calcium chloride, CaCl2? Calcium chloride, CaCl2
B.) 5.0 g of sodium chloride, NaCl, or 5.0 g of sodium fluoride, NaF? Sodium fluoride, NaF
C.) 2.0 g of iron oxide, FeO, or 2.0 g of iron sulfide, FeS? Iron oxide, FeO
7.) What is the mass of 5 mol of iron (III) oxide, Fe2O3?
Mass of iron: 55.8, x2 = 111.6 g
Mass of oxygen: 15.9, x3= 47.7 g
111.6 g + 47.7 g = 159.3 g <--- ONE MOLE
159.3 g x 5 moles = 796.5 g
Scientists use scientific notation to express numbers that are very big or very small. Correct scientific notation has only 1 digit before the decimal point! We've studied the use of scientific notation to express how many molecules are in a test sample. Once again, we looked at moles. One mole, 602 sextillion, is written in scientific notation as 6.022 x 10^23. The term "molar mass" refers to how much of a substance is needed to achieve 1 mole of molecules. The molar masses for all the known elements are the same as the atomic masses on the periodic table. Molar mass helps scientists convert between moles of atoms and grams of atoms. That's where the two tables I mentioned in lesson 7 come into play.
Problems:
4.) Give the molar mass for these elements:
A.) nitrogen, N - 14.0 g
B.) neon, Ne - 20.2 g
C.) chlorine, Cl - 35.5 g
D.) copper, Cu - 63.5 g
6.) Which contains more atoms?
A.) 12 g of hydrogen, H, or 12 g of carbon, C? 12 g of hydrogen. Hydrogen has the smaller molar mass.
B.) 27 g of aluminum, Al, or 27 g of iron, Fe? 27 g of aluminum. Aluminum has the smaller molar mass.
C.) 40 g of calcium, Ca, or 40 g of sodium, Na? 40 g of sodium. Sodium has the smaller molar mass.
D.) 40 g of calcium, Ca, or 40 g of zinc, Zn? 40 g of calcium. Calcium has the smaller molar mass.
E.) 10 g of lithium, Li, or 100 g of lead, Pb? 100 g of Pb, because it has the larger sample size.
Lesson 10:
Because individual atoms cannot be counted easily by themselves, scientists compare moles of substances rather than masses of substances. If one was given 50 moles of one element and 50 moles of another, their molar masses are significant, but only in telling which element would be lighter. Then, it's up to us to decide which sample is larger based off of how many more/less atoms it takes to make an equal sample. If given a compound, where the molar mass isn't clear but rather a bunch of molar masses thrown together, one must add the masses of each element in the compound, multiply by the subscripts (if there are any) and add all the masses together to find the compound's whole mass.
Problems:
5.) Which has more moles of metal atoms?
A.) 10.0 g of calcium, Ca, or 10.0 g of calcium chloride, CaCl2? Calcium chloride, CaCl2
B.) 5.0 g of sodium chloride, NaCl, or 5.0 g of sodium fluoride, NaF? Sodium fluoride, NaF
C.) 2.0 g of iron oxide, FeO, or 2.0 g of iron sulfide, FeS? Iron oxide, FeO
7.) What is the mass of 5 mol of iron (III) oxide, Fe2O3?
Mass of iron: 55.8, x2 = 111.6 g
Mass of oxygen: 15.9, x3= 47.7 g
111.6 g + 47.7 g = 159.3 g <--- ONE MOLE
159.3 g x 5 moles = 796.5 g
Unit 4, Lessons 7 and 8
Lesson 7:
The lethal dose of a substance, also referred to as its LD50, is the amount of substance that it takes to kill 50% of test specimens. All substances have their own LD50, and that number corresponds to kilograms, which means that the amount it takes for a toxin to be very harmful might be more or less. As LD50 increases, so does the amount needed, and vice versa. The truth is, everything on Earth is a toxin, even water and sugar. However, in moderation, some substances, such as vitamins, can be therapeutic and helpful to the body's processes.
Problems:
4.) Ethanol is grain alcohol. The LD50 for ethanol is 7060 mg/kg (rat, oral).
A.) How many milligrams of ethanol would be lethal to a 132 lb adult?
B.) How many glasses containing 13,000 mg of ethanol would be lethal to a 22 lb child?
132 lbs. | 1 kg | 1510 mg
-------------------------- = 90,600 mg would be lethal
2.2 lbs. | 1 kg
Lesson 8:
We've already discussed the mole, and know that 602 sextillion atoms = 1 mole. The mole is just a fancy unit used to measure incredibly large amounts of small objects. One can find how many moles of a substance are present in a sample if they have the molar mass (in grams) of the substance, and the amount of grams of sample that they have. It works the other way around, as well, as illustrated here:
x moles (sample) | y grams
---------------------------------------------------- = # of grams
| 1 mole (molar mass)
Scientists weigh large amounts of small objects using mass and basic operations because it isn't possible to count atoms individually. If they are oh-so-curious scientists who want to find out how off their results are, they find percent error, represented by this formula:
The lethal dose of a substance, also referred to as its LD50, is the amount of substance that it takes to kill 50% of test specimens. All substances have their own LD50, and that number corresponds to kilograms, which means that the amount it takes for a toxin to be very harmful might be more or less. As LD50 increases, so does the amount needed, and vice versa. The truth is, everything on Earth is a toxin, even water and sugar. However, in moderation, some substances, such as vitamins, can be therapeutic and helpful to the body's processes.
Problems:
4.) Ethanol is grain alcohol. The LD50 for ethanol is 7060 mg/kg (rat, oral).
A.) How many milligrams of ethanol would be lethal to a 132 lb adult?
132 lbs. | 1 kg | 7060 mg
-------------------------- = 423, 600 mg would be lethal
2.2 lbs. | 1 kg
22 lbs. | 1 kg | 7060 mg
---------------------------- = 70,600 mg
| 2.2 lbs. | 1 kg
70,600 mg / 13,000 mg = 5.43, or about 5 glasses.
5.) The LD50 for Vitamin A is 1510 mg/kg (rat, oral).
A.) How many mg of vitamin A would be lethal to a 132 lb adult?
-------------------------- = 90,600 mg would be lethal
2.2 lbs. | 1 kg
B.) How many vitamin tablets containing 0.40 mg of vitamin A would be lethal to an adult?
90,600 mg / 0.40 mg = 226, 500 tablets
We've already discussed the mole, and know that 602 sextillion atoms = 1 mole. The mole is just a fancy unit used to measure incredibly large amounts of small objects. One can find how many moles of a substance are present in a sample if they have the molar mass (in grams) of the substance, and the amount of grams of sample that they have. It works the other way around, as well, as illustrated here:
x grams (sample) | 1 mole
------------------------------------------------------ = # of moles
| y grams (molar mass)
---------------------------------------------------- = # of grams
| 1 mole (molar mass)
Scientists weigh large amounts of small objects using mass and basic operations because it isn't possible to count atoms individually. If they are oh-so-curious scientists who want to find out how off their results are, they find percent error, represented by this formula:
estimated value - actual value
---------------------------------------------- x 100
actual value
Problems:
8.) What is the mass, in grams, of one copper atom? About 64 g if you rounded, 63.54 if you didn't.
10.) Suppose you have 50 grams of copper and 50 grams of gold. Which of these has more atoms? Explain. Since the mass of one copper atom is roughly 64 and the mass of a gold atom is about 170, a 50 g sample of copper has more atoms. Since the samples are equal in size, it takes more, lighter copper atoms to equal as many gold atoms.
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