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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