2Na + 2H2O = 2NaOH + H2

Calculat the moles and volume of hydrogen produced when 0.2 moles of sodium reacts with excess water.

2 answers

You know the ratio for the moles of sodium to hydrogen from the equation is 2:1 so you can work out the moles of hydrogen. The volume will depend on the temperature and pressure. 1 mole of gas at 25 degrees C and 1 atmosphere pressure has a volume of 24.465 L.
Here is a worked example of a stoichiometry problem.
http://www.jiskha.com/science/chemistry/stoichiometry.html