Calculate the mass and volume of hydrogen obtained when 4.6 g of sodium is completely “dissolved” in water.

Given:
m (Na) = 4.6 g;
To find:
m (H2) -?
V (H2) -?
Decision:
1) We compose the reaction equation typical for this problem:
2Na + H2O = Na2O + H2;
2) Find the amount of sodium in 4.6 grams of metal:
n (Na) = m: M = 4.6 g: 23 g / mol = 0.2 mol;
3) We compose logical equality:
if 2 mol of Na gives 1 mol of H2,
then 0.2 mol Na will give x mol H2,
then x = 0.1 mol.
4) Find the mass of the released hydrogen:
m (H2) = n * M = 0.1 mol * 2 g / mol = 0.2 g;
5) Find the volume of hydrogen:
V (H2) = n * Vm = 0.2 mol * 22.4 L / mol = 4.48 L.
Answer: m (H2) = 0.2 g; V (H2) = 4.48 liters.