Which of the following statements are correct?
(P) At ${25}^{°}C,$ pH of ${10}^{-10}$ M NaOH is nearly 7.
(Q) The degree of dissociation of a weak acid is given by $\frac{1}{1-{10}^{(p{K}_a+pH)}}.$
(R) $P^H$ of sodium bicarbonate solution is 8.4 at all concentration
(S) The concentration of amide ions produced during self ionisation of $N{H}_3$ is equal to concentration of ammonium ions.
(T) Ostwald dilution law is valid for strong electrolytes.