Which of the following will be more soluble in an acidic solution than in pure water?

AgI, Ni(OH)2, KClO4, SrSO4, CaCO3

Ni(OH)2

Well, let me think about this... Ah, I've got it! The answer is CaCO3 because when things get a little acid-y, calcium carbonate gets more dissolvable. It's like it's doing the acid dance, thinking "I'm soluble now, baby!" while the others are still hanging out in pure water, feeling left out. Poor things, they just can't catch a break!

To determine which substance will be more soluble in an acidic solution than in pure water, we need to consider the solubility rules and the effects of acidity on solubility.

Solubility rules state that most sulfate (SO4^2-) salts and carbonate (CO3^2-) salts are insoluble in water. However, the solubility of these salts can be affected by the presence of an acidic solution.

Acidic solutions contain excess hydrogen ions (H+). These hydrogen ions can react with specific anions in a salt and form a soluble product, making the salt more soluble in an acidic solution.

Let's evaluate each of the given substances:

1. AgI (Silver Iodide): According to solubility rules, AgI is insoluble in water. However, it does not have any specific anions that can react with hydrogen ions to become more soluble in an acidic solution. Therefore, AgI is not expected to be more soluble in an acidic solution than in pure water.

2. Ni(OH)2 (Nickel Hydroxide): According to solubility rules, hydroxide (OH-) salts are insoluble except for those of alkali metals and ammonium. Ni(OH)2 is not expected to be soluble in water. In acidic solutions, the hydrogen ions from the acid can react with the hydroxide ions (OH-) to form water, thereby decreasing the concentration of hydroxide ions and increasing the solubility of the nickel hydroxide. Therefore, Ni(OH)2 is expected to be more soluble in an acidic solution than in pure water.

3. KClO4 (Potassium Perchlorate): Perchlorate salts are generally soluble in water, including KClO4. The solubility of potassium perchlorate is not influenced significantly by changes in acidity. Therefore, KClO4 is expected to have similar solubility in both an acidic solution and pure water.

4. SrSO4 (Strontium Sulfate): According to solubility rules, sulfates are mostly insoluble in water, including SrSO4. In an acidic solution, hydrogen ions can react with sulfate ions (SO4^2-) to form sulfuric acid, which is a stronger acid. This reaction reduces the concentration of sulfate ions, making SrSO4 slightly more soluble in an acidic solution than in pure water. Therefore, SrSO4 is expected to be slightly more soluble in an acidic solution.

5. CaCO3 (Calcium Carbonate): According to solubility rules, carbonates are generally insoluble in water. In an acidic solution, the carbonate ions (CO3^2-) can react with hydrogen ions to form carbonic acid, which is unstable and decomposes to produce carbon dioxide gas (CO2) and water. This reaction consumes carbonate ions, resulting in an increased solubility of calcium carbonate in an acidic solution compared to pure water. Thus, CaCO3 is expected to be more soluble in an acidic solution.

In summary, the substances that are expected to be more soluble in an acidic solution than in pure water are Ni(OH)2 and CaCO3.

The secret to these is knowing what anions react with H^+ (the acid) and if any weak acids or precipitates are formed.

For AgI the acid would be HI and that is a strong acid; therefore, AgI is NOT more soluble in acid than in water.

For Ni(OH)2, adding H^+ reacts with OH to form H2O so YES, it is more soluble in acid than in H2O

For KClO4, adding H^+ forms HClO4 but that is a strong acid so it is NOT more soluble in acid.

SrSO4 would be HSO4^- and that is k2 for H2SO4 so YES.

CaCO3 would be HCO3^- which is k2 for H2CO3 and YES.