The concentration of an aqueous $HCl$ solution is $10^{-9} \ N$. What is the $pH$ of the solution?

$0.1 \ (M) \ HCl$ and $0.1 \ (M) \ H_2SO_4$ each of volume $2 \ mL$ are mixed and the volume is made up to $6 \ mL$ by adding $2 \ mL$ of $0.01 \ (N) \ NaCl$ solution. The $pH$ of the resulting mixture is

$pH$ value of $0.001 \ M \ NaOH$ solution is $..... .$

The $pH$ of $0.01 \ N$ lime water is:

$1 \ L$ of $0.02 \ M$ aqueous $HCl$ is mixed with $1 \ L$ of $0.01 \ M$ aqueous $H_2SO_4$ solution. Assuming complete dissociation and no change in the volume upon mixing,the $pH$ of the resultant solution is $(\log_{10} 2 = 0.3)$.

$10^{-6} \ M \ NaOH$ is diluted $100$ times. The $pH$ of the diluted base is