Write the balanced NET IONIC equation for the reaction that occurs when hydrocyanic acid and...

• The hydrocyanic acid reacts with potassium hydroxide to form potassium cyanide and water. The corresponding reaction is shown below.

{eq}{\rm{HCN}}\left( {{\rm{aq}}} \right) + {\rm{KOH}}\left( {{\rm{aq}}} \right) \to {\rm{KCN}}\left( {{\rm{aq}}} \right) + {{\rm{H}}_2}{\rm{O}}\left( l \right) {/eq}

The hydrocyanic acid is a weak acid and does not dissociate completely. Potassium hydroxide is a strong base and dissociates completely. The ionic equation of the above reaction is shown below.

{eq}{\rm{HCN}}\left( {{\rm{aq}}} \right) + {{\rm{K}}^ + }\left( {{\rm{aq}}} \right) + {\rm{O}}{{\rm{H}}^ - }\left( {{\rm{aq}}} \right) \to {{\rm{K}}^ + }\left( {{\rm{aq}}} \right) + {\rm{C}}{{\rm{N}}^ - }\left( {{\rm{aq}}} \right) + {{\rm{H}}_2}{\rm{O}}\left( l \right) {/eq}

Here, {eq}{{\rm{K}}^ + }\left( {{\rm{aq}}} \right)\;\rm and\;{\rm{C}}{{\rm{N}}^ - }\left( {{\rm{aq}}} \right) {/eq} ions act as spectator ions. Therefore, the net ionic equation for the given reaction is shown below.

{eq}\boxed{\;{\rm{H^+}}\left( {{\rm{aq}}} \right) + {\rm{O}}{{\rm{H}}^ - }\left( {{\rm{aq}}} \right) \to {{\rm{H}}_2}{\rm{O}}\left( l \right)\;} {/eq}

• Hydrocyanic acid is a weak acid whereas potassium hydroxide is the strong base. The product of the reaction is salt and water. Therefore, the reaction is classified as weak acid + strong base.

Therefore, option (B) is the correct option.

• As potassium hydroxide is the strong base, so it neutralizes weak acid (HCN) completely. Therefore, the extent of the reaction is 100%.

Hence, the correct option is option (D).