Why does an aqueous solution of an acid conduct electricity?

Plaster of Paris should be stored in a moisture-proof container. Explain why?

Why do $HCl$,$HNO_3$,etc.,show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

Write word equations and then balanced chemical equations for the reactions taking place when:
$(a)$ Dilute sulphuric acid reacts with aluminium powder.
$(b)$ Dilute hydrochloric acid reacts with iron filings.

Five solutions $A, B, C, D$ and $E$ when tested with universal indicator showed $pH$ values of $4, 1, 11, 7$ and $9$,respectively. Which solution is:
$(a)$ neutral?
$(b)$ strongly alkaline?
$(c)$ strongly acidic?
$(d)$ weakly acidic?
$(e)$ weakly alkaline?
Arrange the $pH$ values in increasing order of hydrogen-ion concentration.