How many grams of water vapor are formed?

Question

A hydrogen-filled balloon is ignited, and 1.40 g of hydrogen react with 11.2 g of oxygen. How many grams of water vapor are formed? (Assume that water vapor is the only product.)

Answer 1

Since water vapor is the only product and you have 8 times the mass of O2 as H2 (1.40*8= 11.2), together they combine to make 1.40 + 11.2 = 12.6 g water vapor and there is not a limiting element with some left over.