Question

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compare the solubility of zinc carbonate in each of the following aqueous solutions:

0.10 m zn(no₃)₂
0.10 m k₂co₃
0.10 m kno₃
0.10 m nh₄ch₃coo

more soluble than in
pure water.
similar solubility as in
pure water.
less soluble than in
pure water.
clear all

Explanation:

To solve this, we analyze the solubility of \( \text{ZnCO}_3 \) using the common ion effect and salt hydrolysis:

Step 1: Analyze \( 0.10 \, \text{M} \, \text{Zn(NO}_3\text{)}_2 \)

\( \text{Zn(NO}_3\text{)}_2 \) dissociates into \( \text{Zn}^{2+} \) and \( \text{NO}_3^- \). \( \text{ZnCO}_3 \) dissociates as \( \text{ZnCO}_3(s)
ightleftharpoons \text{Zn}^{2+}(aq) + \text{CO}_3^{2-}(aq) \). The common ion \( \text{Zn}^{2+} \) from \( \text{Zn(NO}_3\text{)}_2 \) shifts the equilibrium left, decreasing solubility. So, less soluble than pure water.

Step 2: Analyze \( 0.10 \, \text{M} \, \text{K}_2\text{CO}_3 \)

\( \text{K}_2\text{CO}_3 \) dissociates into \( \text{K}^+ \) and \( \text{CO}_3^{2-} \). The common ion \( \text{CO}_3^{2-} \) from \( \text{K}_2\text{CO}_3 \) shifts the \( \text{ZnCO}_3 \) equilibrium left, decreasing solubility. Less soluble than pure water.

Step 3: Analyze \( 0.10 \, \text{M} \, \text{KNO}_3 \)

\( \text{KNO}_3 \) dissociates into \( \text{K}^+ \) and \( \text{NO}_3^- \), no common ions with \( \text{ZnCO}_3 \). Also, \( \text{KNO}_3 \) is a neutral salt, so no hydrolysis affecting \( \text{Zn}^{2+} \) or \( \text{CO}_3^{2-} \). Solubility similar to pure water.

Step 4: Analyze \( 0.10 \, \text{M} \, \text{NH}_4\text{CH}_3\text{COO} \)

\( \text{NH}_4^+ \) hydrolyzes: \( \text{NH}_4^+ + \text{H}_2\text{O}
ightleftharpoons \text{NH}_3 + \text{H}_3\text{O}^+ \), and \( \text{CH}_3\text{COO}^- \) hydrolyzes: \( \text{CH}_3\text{COO}^- + \text{H}_2\text{O}
ightleftharpoons \text{CH}_3\text{COOH} + \text{OH}^- \). The \( \text{H}_3\text{O}^+ \) from \( \text{NH}_4^+ \) hydrolysis reacts with \( \text{CO}_3^{2-} \) (from \( \text{ZnCO}_3 \) dissociation): \( \text{CO}_3^{2-} + \text{H}_3\text{O}^+
ightleftharpoons \text{HCO}_3^- + \text{H}_2\text{O} \), shifting \( \text{ZnCO}_3 \) equilibrium right, increasing solubility. More soluble than pure water.

Answer:

• \( 0.10 \, \text{M} \, \text{Zn(NO}_3\text{)}_2 \): Less soluble than in pure water.
• \( 0.10 \, \text{M} \, \text{K}_2\text{CO}_3 \): Less soluble than in pure water.
• \( 0.10 \, \text{M} \, \text{KNO}_3 \): Similar solubility as in pure water.
• \( 0.10 \, \text{M} \, \text{NH}_4\text{CH}_3\text{COO} \): More soluble than in pure water.