posted by Noah .
2Na + 2H2O = 2NaOH + H2
Calculat the moles and volume of hydrogen produced when 0.2 moles of sodium reacts with excess water.
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.