Question

given the rule that all compounds containing li⁺, na⁺, k⁺, nh₄⁺, no₃⁻, and c₂h₃o₂⁻ ions are soluble, which of the following is insoluble?
○ libr
○ nano₃
○ ca(c₂h₃o₂)₂
○ caco₃

Explanation:

Step1: Analyze LiBr

LiBr contains \( \text{Li}^+ \) ion. According to the rule, compounds with \( \text{Li}^+ \) are soluble. So LiBr is soluble.

Step2: Analyze \( \text{NaNO}_3 \)

\( \text{NaNO}_3 \) contains \( \text{Na}^+ \) and \( \text{NO}_3^- \) ions. Both ions are in the soluble rule list, so \( \text{NaNO}_3 \) is soluble.

Step3: Analyze \( \text{Ca(C}_2\text{H}_3\text{O}_2\text{)}_2 \)

\( \text{Ca(C}_2\text{H}_3\text{O}_2\text{)}_2 \) contains \( \text{C}_2\text{H}_3\text{O}_2^- \) (acetate) ion. Compounds with \( \text{C}_2\text{H}_3\text{O}_2^- \) are soluble, so this compound is soluble.

Step4: Analyze \( \text{CaCO}_3 \)

\( \text{CaCO}_3 \) contains \( \text{Ca}^{2+} \) and \( \text{CO}_3^{2-} \) ions. Neither \( \text{Ca}^{2+} \) (except with specific ions) nor \( \text{CO}_3^{2-} \) (except with \( \text{Li}^+,\text{Na}^+,\text{K}^+,\text{NH}_4^+ \)) are in the soluble rule list. So \( \text{CaCO}_3 \) is insoluble.

Answer:

\( \text{CaCO}_3 \) (the option with \( \text{CaCO}_3 \))