Question

Ammonia can be dried by

• A. Conc. $H_{2}S{O}_4$
• B. $P_4{O}_{10}$
• C. $CaO$
• D. Anhydrous $CaC{l}_2$

Answer 1

The correct option is C $CaO$

Concentrated $H_{2}S{O}_4,$ anhydrous $CaC{l}_2$ and $P_4{O}_{10}$ are not used to dry ammonia because $N{H}_3$ is basic and will react with them.
$N{H}_3+Conc.H_{2}S{O}_4\to (N{H}_4{)}_{2}S{O}_4$
$N{H}_3+P_4{O}_{10}\to (N{H}_4{)}_{3}P{O}_4$

$N{H}_3+CaC{l}_2\to CaC{l}_2.8N{H}_3$
The gas is passed through fresh quicklime (solid CaO lumps) to effectively dry it.