Find pH

Rank the following in terms of acidity: HClO, IOH, and HBrO. Explain the trend.

Rank the following in terms of acidity: HClO, HClO$_2$, HClO$_3$, HClO$_4$. Explain the trend.

Calculate the pH of a 0.2 M solution of NH$_4$Br, K$_a$ = 5.6 x 10$^{-10}$

Compare the concentration of H$_3$O$^+$ in 1 M and 2 M solutions of HC$_2$H$_3$O$_2$, K$_a$ = 1.8 x 10$^{-5}$. (doubling the concentration results in an increase of hydronium ions by what factor?)