The solubility rules listed in table below.
General Rules for Solubility of Ionic Compounds (Salts) in Water at 25 °C.
- Most nitrate (NO3) salts are soluble.
- Most salts of Na+, K+, and NH4+ are soluble.
- Most chloride salts are soluble. Notable exceptions are AgCl, PbCl2, and Hg2 Cl2.
- Most sulfate salts are soluble. Notable exceptions are BaSO4, PbSO4, and CaSO4.
- Most hydroxide compounds are only slightly soluble. The important exceptions are NaOH and KOH. Ba(OH)2 and Ca(OH)2 are only moderately soluble.
- Most sulfide (S2), carbonate (CO3), and phosphate (PO4) salts are only slightly soluble.*
*The terms insoluble and slightly soluble really mean the same thing: such a tiny amount dissolves that it is not possible to detect it with the naked eye.
a On the basis of the general solubility rules, which choice explains why sodium sulfide would be expected to be appreciably soluble in water.
Most sulfide (S2) salts are only slightly soluble.
Most salts of Nat are insoluble.
Most sulfide (S2) salts are soluble.
Most salts of Nat are soluble
bOn the basis of the general solubility rules, which choice explains why iron(II) nitrate would be expected to be appreciably soluble in water.
Most nitrate salts are soluble.
Most salts of Fe2+ are soluble.
Most nitrate salts are insoluble.
Most salts of Fe2+ are insoluble.
The Correct Answer and Explanation is :
Question a: Why sodium sulfide would be expected to be appreciably soluble in water.
Answer: Most salts of Na+ are soluble.
Explanation:
Sodium sulfide (Na2S) is expected to be appreciably soluble in water based on the general solubility rule that “most salts of Na+ are soluble.” According to this rule, salts formed with sodium (Na+) ions tend to dissolve easily in water. Sodium ions, as alkali metal cations, form strong ionic bonds with anions such as sulfide (S²⁻), making it easy for them to dissociate in water. This high solubility arises because sodium, as a highly reactive alkali metal, readily dissolves in water, ensuring that its associated ions, including sulfide ions, separate and disperse in the solution.
Even though sulfide salts (S²⁻) are generally considered to be slightly soluble according to the solubility rules, sodium sulfide is an exception. Sodium ions, as part of the alkali metals group, do not form insoluble compounds with sulfide ions, unlike some other metal cations. The solubility of sodium sulfide is therefore driven by the solubility of sodium salts in water, and the sulfide ions dissociate in solution, making the compound appreciably soluble.
Thus, the rule that “most salts of Na+ are soluble” directly explains why sodium sulfide is expected to dissolve easily in water, even though sulfide salts are typically less soluble. Sodium salts are among the few that defy the general trend for sulfide solubility.
Question b: Why iron(II) nitrate would be expected to be appreciably soluble in water.
Answer: Most nitrate salts are soluble.
Explanation:
Iron(II) nitrate (Fe(NO₃)₂) is expected to be appreciably soluble in water due to the general solubility rule stating that “most nitrate salts are soluble.” Nitrate (NO₃⁻) is a highly soluble ion, and salts containing this ion tend to dissolve easily in water. This is true for almost all nitrate salts, regardless of the cation involved.
Iron(II) nitrate is composed of Fe²⁺ (iron(II)) ions paired with nitrate ions. Even though Fe²⁺ is not always soluble in water when it forms salts with other anions (for example, some iron(II) salts like iron(II) carbonate or iron(II) hydroxide are less soluble), the nitrate anion is an exception. Nitrate ions are known for their ability to form highly soluble salts, which is why iron(II) nitrate, like most nitrate salts, dissolves well in water.
In this case, the solubility is governed primarily by the nitrate ion, which overrides the tendency of iron(II) to form less soluble compounds with other anions. Therefore, iron(II) nitrate dissolves easily in water, consistent with the solubility rule that “most nitrate salts are soluble.”
In conclusion, the solubility of iron(II) nitrate in water can be attributed to the highly soluble nature of nitrate salts, making it an easy-to-dissolve compound.