An aqueous solution of $HCl$ has a $pH$ of $2.0$. When water is added to increase the $pH$ to $5.0$,the hydrogen ion concentration

At $90\,^oC$,the $pH$ of a $0.1\,M$ $NaCl$ aqueous solution 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,$6.4$

The $pH$ of a solution is $9.5$. The solution is

If the $pH$ of a soft drink is $3.7$,what is the concentration of hydrogen ions?

The value of the ion product constant for water,$(K_w)$ at $60\,^{\circ}C$ is $9.6 \times 10^{-14} \,M^2$. What are the $[H_3O^{+}]$ of a neutral aqueous solution at $60\,^{\circ}C$ and the nature of an aqueous solution with a $pH = 7.0$ at $60\,^{\circ}C$,respectively?