Define pH. Calculate the pH of 0.001 M of HCl

Calculate the pH of 0.01 M solution of CH_(3)COOH.K_(a) for CH_(3)COOH at 298K is 1.8xx10^(-5)

If the equlibrium constant for the reaction of weak acid HA with strong base is 10^(9) then calculate the pH of 0.1 M NaA.