What will be the action of the following substances on litmus paper? Dry $HCl$ gas,Moistened $NH_3$ gas,Lemon juice,Carbonated soft drink,Curd,Soap solution.

(N/A) The action of these substances on litmus paper depends on their acidic or basic nature. Acids turn blue litmus red,while bases turn red litmus blue. Dry $HCl$ gas does not show acidic properties because it lacks $H^+$ ions in the absence of water. Moistened $NH_3$ gas acts as a base $(NH_4OH)$. Lemon juice,carbonated soft drinks,and curd are acidic. Soap solution is basic.

Substance	Action on Litmus paper
Dry $HCl$ gas	No change
Moistened $NH_3$ gas	Turns red to blue
Lemon juice	Turns blue to red
Carbonated soft drink	Turns blue to red
Curd	Turns blue to red
Soap solution	Turns red to blue