Why does dry $HCl$ gas not change the colour of the dry litmus paper?

Under what soil condition do you think a farmer would treat the soil of his fields with quick lime $(CaO)$,slaked lime $(Ca(OH)_2)$,or chalk $(CaCO_3)$?

Equal lengths of magnesium ribbons are taken in test tubes $A$ and $B$. Hydrochloric acid $(HCl)$ is added to test tube $A$,while acetic acid $(CH_3COOH)$ is added to test tube $B$. The amount and concentration taken for both the acids are the same. In which test tube will the fizzing occur more vigorously and why?

Metal compound $A$ reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

Name the sodium compound which is used for softening hard water.

Why does an aqueous solution of an acid conduct electricity?