What is the ratio of the number of $H^{+}$ ions to the number of $H_2O$ molecules in $1 \ L$ of water?

When $10 \, mL$ of $0.1 \, M$ acetic acid $(pK_a = 5.0)$ is titrated against $10 \, mL$ of $0.1 \, M$ ammonia solution $(pK_b = 5.0)$,the equivalence point occurs at $pH$:

Which of the following statement$(s)$ is/are correct?
$ (A) $ The $pH$ of $1 \times 10^{-8} \ M \ HCl$ solution is $8$.
$ (B) $ The conjugate base of $H_2PO_4^{-}$ is $HPO_4^{2-}$.
$ (C) $ $K_w$ increases with increase in temperature.
$ (D) $ When a solution of weak monoprotic acid is titrated against a strong base at half neutralisation point,$pH = pK_a$.
Choose the correct answer from the option given below.

Equal volumes of three acid solutions with $pH$ values of $3, 4,$ and $5$ are mixed. What will be the concentration of $H^+$ ions in the resulting mixture?

Which of the following statement(s) is(are) correct?

At $25^{\circ} C$, the molar conductance of $0.007 \ M$ hydrofluoric acid is $150 \ \text{mho} \ cm^{2} \ mol^{-1}$ and its $\Lambda_{m}^{\circ} = 500 \ \text{mho} \ cm^{2} \ mol^{-1}$. The value of the dissociation constant of the acid at the given concentration at $25^{\circ} C$ is