Why does an aqueous solution of an acid conduct electricity?

$10 \,mL$ of a solution of $NaOH$ is found to be completely neutralized by $8 \,mL$ of a given solution of $HCl$. If we take $20 \,mL$ of the same solution of $NaOH$,the amount of $HCl$ solution (the same solution as before) required to neutralize it will be ...... $mL$.

What is a neutralization reaction? Give two examples.

$A$ solution turns red litmus blue,its $pH$ is likely to be

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?

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.