Which of the following is acidic in nature?

What is the $pH$ value of a basic aqueous solution?

Write true or false for the following statement:
The process of dissolving an acid or a base in water is a highly exothermic process.

How do metal carbonates and metal hydrogen carbonates react with acids? Give their chemical equations. Name the gas evolved during the reaction. What will happen when this gas is passed through lime water?

What happens when a solution of an acid is mixed with a solution of a base in a test tube?
$(i)$ The temperature of the solution increases
$(ii)$ The temperature of the solution decreases
$(iii)$ The temperature of the solution remains the same
$(iv)$ Salt formation takes place

Acid + Metal oxide $\longrightarrow$ ?