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

Observe the following solutions:
$I$. Black coffee
$II$. $0.2 \ M \ NaOH$
$III$. Lemon juice
$IV$. Lime water
$V$. Human Saliva
$VI$. Tomato juice
The number of solutions with $pH$ less than $7$ is

At $90\, ^\circ C$ pure water has $[H_3O^{+}] = 10^{-6}\, mol\, L^{-1}$. The value of $K_w$ at $90\, ^\circ C$ is

When $NaCl$ is dissolved in water,the sodium ion undergoes ......... .

At $90\,^{\circ}C$,pure water has $H_3O^{+}$ ion concentration of $10^{-6}\,mol\,L^{-1}$. The $K_w$ at $90\,^{\circ}C$ is

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