Question

Which of the following substances are likely to be soluble in water? (a) \(\mathrm{Ag}_{2} \mathrm{O}\) (b) \(\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}\) (c) \(\mathrm{SnCO}_{3}\) (d) \(\mathrm{Al}_{2} \mathrm{~S}_{3}\)

Short answer

(b) \(\mathrm{Ba\left(NO_3\right)_2}\) is likely soluble in water.

Step-by-step solution

Understanding Solubility Rules

To determine which substances are soluble in water, we need to apply the common solubility rules. Nitrates (NO3-) are generally soluble, as are alkali metal salts and certain sulfates. Conversely, many carbonates, oxides, and sulfides are insoluble except when paired with certain cations such as alkali metals or ammonium.

Evaluating Silver(I) Oxide, \( \mathrm{Ag}_{2} \mathrm{O} \)

Silver(I) oxide is generally insoluble in water. The oxides of most metals are insoluble unless they are alkali metal oxides.

Evaluating Barium Nitrate, \( \mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2} \)

Barium nitrate is likely to be soluble in water due to the nitrate ion \( \left(\mathrm{NO}_{3}^{-}\right)\), which is universally soluble according to solubility rules.

Evaluating Tin(II) Carbonate, \( \mathrm{SnCO}_{3} \)

Most carbonates, including tin(II) carbonate, are insoluble in water, except when they are salts of alkali metals or ammonium.

Evaluating Aluminum Sulfide, \( \mathrm{Al}_{2} \mathrm{~S}_{3} \)

Upon reaction with water, aluminum sulfide hydrolyzes to form aluminum hydroxide and hydrogen sulfide gas, showing limited solubility as aluminum sulfide itself does not readily dissolve in water.

Key concepts

Nitrate Solubility

Nitrates (\(\text{NO}_3^-\)) are one of the most universally soluble ions in the chemical world. This means that any compound containing the nitrate ion is very likely to dissolve in water. This characteristic makes nitrates quite unique and valuable for chemical reactions and industrial applications.
Here are a few points to remember about nitrate solubility:

• Nitrates do not hesitate to dissolve whether paired with metals, nonmetals, or even complex ions.
• The universal solubility of nitrate ions is due to their stable electron configuration, which prevents interactions that would inhibit dissolution.
• Whether it's barium nitrate or another, you can usually count on nitrate compounds to be water-soluble.

Carbonate Solubility

Carbonates (\(\text{CO}_3^{2-}\)), on the other hand, tend to have limited solubility in water. Most carbonate compounds do not dissolve well, except those involving alkali metals or ammonium ions.
Here are some highlights about carbonate solubility:

• Alkali metal carbonates, like sodium carbonate, easily dissolve because of high reactivity and solubility of alkali metals.
• Non-alkali metal carbonates like tin(II) carbonate (\(\text{SnCO}_3\)) are usually insoluble.
• This limited solubility is important for natural processes and is utilized in applications where water resistance is necessary, such as construction materials.

Oxide Solubility

The solubility of oxides is typically very low, especially when considering metals other than alkali metals. Most metal oxides do not dissolve in water.
Key points for oxide solubility include:

• Metal oxides like silver(I) oxide (\(\text{Ag}_2\text{O}\)) are usually insoluble in water.
• Exceptions include alkali metal oxides and certain alkaline earth metal oxides, which can react with water to form soluble hydroxides.
• This insolubility can make oxides useful in catalysts and protective coatings.

Sulfide Solubility

Sulfides (\(\text{S}^{2-}\)) are generally not soluble in water, with few exceptions. This holds especially true when combined with metals other than those of the alkali group.
Understanding sulfide solubility involves:

• Aluminum sulfide (\(\text{Al}_2\text{S}_3\)), for instance, does not dissolve in water but reacts with it to form hydrogen sulfide gas and other compounds.
• The formation of hydrogen sulfide highlights the hydrolysis reaction rather than pure dissolution.
• Soluble sulfides are often limited to those that involve alkali metals or ammonium.