Question

Assuming all volume measurements are made
at the same temperature and pressure, what
volume of hydrogen gas is needed to react
completely with 3.75 L of oxygen gas to produce
water vapor?

Answer 1

2H2 + O2 --> 2H2O
When using gases, one may take a shortcut and use volume as if it were mols.
3.75L O2 x (2 mols H2/1 mol O2) = 3.75 x 2/1 = ? L H2.