Questions: Which of the following reactions is an acid-base reaction? A AgNO3(aq) + KF(aq) -> AgF(s) + KNO3(aq) B NH3(aq) + HF(aq) -> NH4+(aq) + F^-(aq) C NO2(aq) + Al(s) -> NH3(g) + AlO2(aq) D CH4(g) + 2 O2(g) -> 2 H2O(g) + CO2(g)

Solution Steps

An acid-base reaction typically involves the transfer of a proton (H⁺) from an acid to a base. In aqueous solutions, this often results in the formation of water and a salt. The key is to identify the presence of an acid and a base in the reactants.

• Reaction A: \(\mathrm{AgNO}_{3}(\mathrm{aq})+\mathrm{KF}(\mathrm{aq}) \rightarrow \mathrm{AgF}(\mathrm{s})+\mathrm{KNO}_{3}(\mathrm{aq})\)
  This is a double displacement reaction where silver fluoride precipitates. No acid or base is involved.

• Reaction B: \(\mathrm{NH}_{3}(\mathrm{aq})+\mathrm{HF}(\mathrm{aq}) \rightarrow \mathrm{NH}_{4}^{+}(\mathrm{aq})+\mathrm{F}^{-}(\mathrm{aq})\)
  Ammonia (\(\mathrm{NH}_3\)) is a base and hydrofluoric acid (\(\mathrm{HF}\)) is an acid. The reaction involves the transfer of a proton from \(\mathrm{HF}\) to \(\mathrm{NH}_3\), forming \(\mathrm{NH}_4^+\) and \(\mathrm{F}^-\).

• Reaction C: \(\mathrm{NO}_{2}(\mathrm{aq})+\mathrm{Al}(\mathrm{s}) \rightarrow \mathrm{NH}_{3}(\mathrm{~g})+\mathrm{AlO}_{2}(\mathrm{aq})\)
  This is a redox reaction, not an acid-base reaction.

• Reaction D: \(\mathrm{CH}_{4}(\mathrm{~g})+2 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+\mathrm{CO}_{2}(\mathrm{~g})\)
  This is a combustion reaction, not an acid-base reaction.

From the analysis, Reaction B involves the transfer of a proton from an acid to a base, which is characteristic of an acid-base reaction.

Final Answer