Question

all of the following compounds are soluble in water except:
nacl
fecl₃
pbcl₂
nh₄cl
cacl₂

Explanation:

Step1: Recall solubility rules for chlorides

Chlorides are generally soluble, except for those of \( \text{Ag}^+ \), \( \text{Pb}^{2+} \), and \( \text{Hg}_2^{2+} \).

Step2: Analyze each compound

• \( \text{NaCl} \): Sodium chloride, \( \text{Na}^+ \) is a group 1 metal ion, so \( \text{NaCl} \) is soluble.
• \( \text{FeCl}_3 \): Iron(III) chloride, chlorides of transition metals (except the exceptions above) are soluble, so \( \text{FeCl}_3 \) is soluble.
• \( \text{PbCl}_2 \): Lead(II) chloride, \( \text{Pb}^{2+} \) is one of the exceptions for chloride solubility, so \( \text{PbCl}_2 \) is insoluble (or has low solubility) in water.
• \( \text{NH}_4\text{Cl} \): Ammonium chloride, ammonium salts are soluble, so \( \text{NH}_4\text{Cl} \) is soluble.
• \( \text{CaCl}_2 \): Calcium chloride, chlorides of group 2 metals (except some, but \( \text{CaCl}_2 \) is soluble) are soluble, so \( \text{CaCl}_2 \) is soluble.

Answer:

\( \text{PbCl}_2 \) (the option with \( \text{PbCl}_2 \))