The $pH$ of water at $25\,^oC$ is nearly

Which of the following does not make any change in $pH$ when added to $10 \ mL$ of dilute $HCl$?

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,$6.4$

$A$ solution whose $pH$ value is less than $7$ will be

At $298 \ K$,the $pH$ of a $NaCl$ solution is $7$. If the solution is heated to $320 \ K$,which of the following statements is correct?

At $90\,^{\circ}C$ pure water has $[H_3O^{+}] = 10^{-6}\,M$. The value of $K_w$ at this temperature will be: