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

Write word equations and then balanced chemical equations for the reactions taking place when:
$(a)$ Dilute sulphuric acid reacts with zinc granules.
$(b)$ Dilute hydrochloric acid reacts with magnesium ribbon.

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?

What is a neutralization reaction? Give two examples.

Why does distilled water not conduct electricity,whereas rain water does?

$10 \,mL$ 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 ...... $mL$.