How many moles of H2 are needed to make 15 moles of H2O?
2mol H2 + 1 mol O2 --> 2 mol H2O

Due tomorrow which would have a lower ph, a 0.1 m solution of a strong base or a weak base? why? which would have a higher ph, a 0.1 m solution of a strong base or a weak base? why?