Question

Name a gas which turns:
Moist red litmus paper blue.

Answer 1

1. The gas is Ammonia,$N{H}_3$.
2. Ammonia gas turns a wet red litmus paper blue. It gives white fumes with moist Hydrogen Chloride gas ($HCl$).

$N{H}_3\left(g\right)+HCI\left(g\right)\to N{H}_{4}CI\left(g\right)$

Ammonia HydrogenChloride AmmoniumChloride(whitefumes)
Ammonia is a gas that turns moist red litmus paper blue.