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

Which of the following is a weak acid?

Identify the compound $X$ on the basis of the reactions given below. Also,write the name and chemical formulae of $A$,$B$ and $C$.

Crystals of a substance changed their colour on heating in a closed test tube but regained it after sometime when they were allowed to cool down. Name the substance and write its formula and explain the phenomenon involved.

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

How would you distinguish between baking powder and washing soda by heating?