If the $pH$ of water is less than ......,the water pipes undergo corrosion.

There are two different solutions, $A$ and $B$. The $pH$ of solution $A$ is $4$. Find the $pH$ of solution $B$ having $[H^+]$ concentration three times that of solution $A$.

The $pH$ of $D_2O$ and $H_2O$ at $298 \ K$ is

Calculate the hydrogen ion concentration in the following biological fluids whose $pH$ are given below:
$(a)$ Human muscle-fluid,$6.83$
$(b)$ Human stomach fluid,$1.2$
$(c)$ Human blood,$7.38$
$(d)$ Human saliva,$6.4$

An alcoholic drink has a $pH = 4.7$. What is the $OH^{-}$ ion concentration of this solution? (Given: $K_w = 10^{-14} \ mol^2/L^2$)

If the ionic product of water $(K_w)$ is $1.96 \times 10^{-14}$ at $35^{\circ} C$, what is its value at $10^{\circ} C$?