Which of the following is a weak acid?

The conjugate base of $NH_3$ is:

The conjugate base of $NH_3$ is

Which are the conjugate bases of the strong acids $HClO_4$,$H_2SO_4$,$HNO_3$,and $HPO_4^{2-}$? Are they strong or weak?

Which is the strongest of the following acids?

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: