What will be the $OH^{-}$ concentration in an aqueous solution having $pH = 8$?

Give the chemical name and formula of:
$(i)$ Soda ash
$(ii)$ Blue vitriol
$(iii)$ Baking soda

If a few drops of a concentrated acid accidentally spill over the hand of a student,what should be done?

Match the acids given in Column $(A)$ with their correct source given in Column $(B)$.

Column $(A)$	Column $(B)$
$(a)$ Lactic acid	$(i)$ Tomato
$(b)$ Acetic acid	$(ii)$ Lemon
$(c)$ Citric acid	$(iii)$ Vinegar
$(d)$ Oxalic acid	$(iv)$ Curd

On what basis are acids classified as strong and weak acids?

When $Zn$ metal is treated with a dilute solution of a strong acid,a gas is evolved,which is utilised in the hydrogenation of oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed.