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MHT CET · Chemistry · Ionic Equilibrium

Which among the following salts turns blue litmus red in its aqueous solution?

  1. A \(\mathrm{NH}_4 \mathrm{CN}\)
  2. B \(\mathrm{NH}_4 \mathrm{~F}\)
  3. C \(\mathrm{CH}_3 \mathrm{COONa}\)
  4. D \(\mathrm{CH}_3 \mathrm{COONH}_4\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\mathrm{NH}_4 \mathrm{~F}\)

Step-by-step Solution

Detailed explanation

In acidic solution blue litmus paper turns red.
* \(\mathrm{NH}_4 \mathrm{~F}\) is a salt of weak acid \(\mathrm{HF}\left(\mathrm{K}_{\mathrm{a}}=7.2 \times 10^{-4}\right)\) and weak base \(\mathrm{NH}_4 \mathrm{OH}\left(\mathrm{K}_{\mathrm{b}}=1.8 \times 10^{-5}\right) \cdot \mathrm{K}_{\mathrm{a}}>\mathrm{K}_{\mathrm{b}}\) the solution of \(\mathrm{NH}_4 \mathrm{~F}\) will be acidic in nature.
* \(\mathrm{NH}_4 \mathrm{CN} \rightarrow\) Basic solution
\(* \mathrm{CH}_3 \mathrm{COONa} \rightarrow\) Basic solution
\(* \mathrm{CH}_3 \mathrm{COONH}_4 \rightarrow\) Neutral solution.