The conjugate base of $NH_3$ is

Which one of the following acids is the weakest?

The $pK_a$ of acetylsalicylic acid (aspirin) is $3.5$. If the $pH$ of human stomach fluid is $2-3$ and the $pH$ of the small intestine fluid is $8$,then aspirin will:

In the equilibrium $HClO_4 + H_2O \rightleftharpoons H_3O^{+} + ClO_4^-$,which of the following statements is correct?

The ionization constants of two bases $AOH$ and $BOH$ are $K_{b1}$ and $K_{b2}$ respectively. Their relationship is $pK_{b1} < pK_{b2}$. Which of the following does not represent the base with the highest $pH$?

When pure water is exposed to atmospheric $CO_2$,it absorbs the gas. What will be its $pH$?