Which of the following,when added to $20 \ mL$ of a $0.01 \ M$ solution of $HCl$,would decrease its $pH$?

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

When $100 \, mL$ of $M/10 \, NaOH$ solution and $50 \, mL$ of $M/5 \, HCl$ solution are mixed,the $pH$ of the resulting solution would be:

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 $pH$:

$A$ certain weak base has a dissociation constant $2 \times 10^{-5}$. The equilibrium constant for its neutralization reaction with a strong acid is

If $0.1 \, M, 100 \, mL$ $NaOH$ solution is mixed with $0.05 \, M, 100 \, mL$ $H_2SO_4$ solution,the $pH$ of the resulting solution is: