One liter of a solution contains 0.120 moles of benzoic acid c6h5cooh (ka = 6.5 x 10-5) and 0.105 moles of sodium benzoate c6h5coona. a) calculate the ph of this solution. b) calculate the ph of the resulting solution after adding 100 ml of 1.20 m solution of naoh to the starting solution; c) calculate the ph of the resulting solution after adding 100 ml of 0.100 m hcl solution to the starting solution.