How many Moles of hydrogen gas would be needed to react with excess carbon dioxide to produce 76.6 moles of water vapor?

The following questions a24 - a26 relate to 100 ml of 0.0150 m solution of benzoic acid (c6h3cooh). ka(c6h3cooh) = 6.4 x 10^-5. what is the ph of the solution after the addition of 1 x 10^-3 moles of naoh? you may assume no volume change to the solution upon addition of the naoh.