Which of the following oxides will NOT dissolve in both dilute hydrochloric acid and \(2 M\) sodium hydroxide solution?
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Correct Answer: Option D
Explanation:
\(PbO , Al _{2} O _{3}, ZnO\) are all amphoteric oxides i.e. they behave as both acids and bases \(PbO _{(5)}+2 HCl _{\text {(aq })} \rightarrow PbCl _{2(\text { aq })}+ H _{2} O _{\text {(5) }}\) (as a base) \(PbO + NaOH + H _{2} O \rightarrow Na _{2} Pb ( OH )_{4(\text { aq })}\) (as an acid) \(Al _{2} O _{3(5)}+6 HCl _{(\text {aq })} \rightarrow 2 AlCl _{3(\text { aq })}+3 H _{2} O _{\text {() })}\) (as a base) \(Al _{2} O _{3}+2 NaOH +3 H _{2} O \rightarrow 2 NaAl ( OH )_{4(\text { aq }}\) (as an acid) \(CaO\) is a basic oxide (oxide of metal) and will react with acid to form salt and water i.e.
\(CaO _{(5)}+2 HCl _{(\text {aq })} \rightarrow CaCl _{2(\text { aq })}+ H _{2} O _{(1)}\)
\(CaO\) will not dissolve in \(NaOH\)
\(PbO , Al _{2} O _{3}, ZnO\) are all amphoteric oxides i.e. they behave as both acids and bases \(PbO _{(5)}+2 HCl _{\text {(aq })} \rightarrow PbCl _{2(\text { aq })}+ H _{2} O _{\text {(5) }}\) (as a base) \(PbO + NaOH + H _{2} O \rightarrow Na _{2} Pb ( OH )_{4(\text { aq })}\) (as an acid) \(Al _{2} O _{3(5)}+6 HCl _{(\text {aq })} \rightarrow 2 AlCl _{3(\text { aq })}+3 H _{2} O _{\text {() })}\) (as a base) \(Al _{2} O _{3}+2 NaOH +3 H _{2} O \rightarrow 2 NaAl ( OH )_{4(\text { aq }}\) (as an acid) \(CaO\) is a basic oxide (oxide of metal) and will react with acid to form salt and water i.e.
\(CaO _{(5)}+2 HCl _{(\text {aq })} \rightarrow CaCl _{2(\text { aq })}+ H _{2} O _{(1)}\)
\(CaO\) will not dissolve in \(NaOH\)