Mention the range of $pH$ value for identification of a base.

Sodium carbonate is a basic salt because it is a salt of :

In a basic aqueous solution,if the concentration of $[OH^-]$ decreases,what happens to the $pH$?

$500 \ ml$ aqueous solution is prepared by dissolving $2$ moles of $HCl$ in water. What will be the molarity of this solution (in $M$)?

Whose acid-base theory can be applied to aqueous and non-aqueous solutions?

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 $H_{2}CO_{3}$ in test tube $B$ in equal amounts.
$(a)$ Identify the test tube showing vigorous reaction.
$(b)$ Give reason to support your answer.
$(c)$ Name the gas liberated in both the test tubes. How will you prove its liberation?