Among the following,the weakest Lewis base is

The enthalpy of neutralization of which of the following acids and bases is nearly $-13.6 \ kcal$?

Which of the following is not a conjugate acid-base pair?

The values of dissociation constants $(K_a)$ of some acids (at $25\,^{\circ}C$) are as follows. Indicate which is the strongest acid in water:
$(A)$ $1.4 \times 10^{-2}$
$(B)$ $1.6 \times 10^{-4}$
$(C)$ $4.4 \times 10^{-10}$
$(D)$ $4.3 \times 10^{-7}$

The strongest Bronsted base among the following anions is:

Which of the following fertilizers increases the acidity of the soil upon regular use?