When a salt of a weak acid and a weak base is dissolved in water at $25\,^{\circ}C$,the $pH$ of the resulting solution will always

$20\,mL$ of $0.1\,M\,NH_{4}OH$ is mixed with $40\,mL$ of $0.05\,M\,HCl$. The $pH$ of the mixture is nearest to. (Given: $K_{b}(NH_{4}OH) = 1 \times 10^{-5}, \log 2 = 0.30, \log 3 = 0.48, \log 5 = 0.69, \log 7 = 0.84, \log 11 = 1.04$) (in $.2$)

$A$ few grams of sodium carbonate $(Na_2CO_3)$ is added to $1 \ L$ of water. What is the $pH$ or $pH$ range of the resultant solution?

On combining which of the following anions with $NH_4^{\oplus}$ will the $pH$ of the resulting salt solution be independent of the concentration?

Which among the following salts turns blue litmus red in its aqueous solution?

If the base ionization constant $(K_b)$ of hydrazine $(N_2H_4)$ is $9.6 \times 10^{-9}$,what is the percentage of hydrolysis of a $0.1 \ M$ solution of the salt $N_2H_5Cl$?