First we calculate the number of moles of Cl2, that is:
moles Cl2 = 1.5*10^10
grams/71 grams/mol = 211267605.633802817 mol = 2.1 * 10 ^ 8 mole = x
So that based on stoichiometry, the number of moles of NaOH =
2x and that of H2 = x mol
mass of NaOH = 4.2*10^8 * 40 =168*10^8 grams = 1.68 * 10^6 kg
= 1.68 metric tons
mass of H2 = 2.1*10^8 * 2 = 4.2*10^8 grams = 0.042 * 10^6 kg
= 0.042 metric tons.