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.

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