How is the concentration of hydroxide ions (OH–) affected when excess base is dissolved in a solution of sodium hydroxide?

While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

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

Why does an aqueous solution of an acid conduct electricity?

Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?