In a basic aqueous solution,what happens to the basicity of the solution as the concentration of $[OH^-]$ increases?

The chemical formulas for Gypsum and Plaster of Paris are,respectively:

Equal lengths of magnesium ribbon are taken in two test tubes $A$ and $B$. $H_{2}SO_{4}$ is added to test tube $A$ and $H_{2}CO_{3}$ is added to test tube $B$ in equal amounts.
$(a)$ Write chemical equations for both the reactions.
$(b)$ Out of the two acids taken above,which one will have a lower $pH$ value and lower $H^{+}$ concentration,respectively?

What happens when sulfur trioxide reacts with water?

What is the concentration of $[OH^-]$ in distilled water at $298 \; K$?

You have two solutions $A$ and $B$. The $pH$ of solution $A$ is $6$ and the $pH$ of solution $B$ is $8$. Which solution has more hydrogen ion concentration? Which one of these is acidic and which one is basic?