What is the pH and pOH of a 0.20 M NaOH solution?

1. The hydronium ion [H3O+] concentration in a vinegar sample has been determined to be 1.6x10^-3 M. What is the pH?
2. Will these aqueous solutions be acidic, basic, or neutral? Which ion causes the pH change? a) NH4Br b)FeCl3 c) K2CO3 d) KClO4 e) NaBr f) MgCl2 g) NaF h) LiNO3
3. The pH of a 0.20 M propionic acid (CH3CH2COOH) solution is 2.79. What is the Ka of the propionic acid?
4. Two unknown acid solutions are both labelled 0.50 M. How do you determine which is the strong acid and which is the weak acid?

Thank you for your help!