Question

A gas that turns moist red litmus blue?

Answer 1

Ammonia (${\mathrm{NH}}_3$) is the gas that turns red litmus paper to blue litmus paper. Litmus paper tests are given as follows-

• The acid turns litmus paper from blue to red.
• The base turns litmus paper from red to blue.

Since ammonia (${\mathrm{NH}}_3$) gas is basic in nature hence it turns red litmus paper into blue litmus paper.