When 2.00 g mixture of Na and Ca reat with water, 1.164 L hydrogen was produced at 300.0 K and 100.0 kPa. What is the percentage of Na in the sample?
The sample contains 50.5 % Na by mass.
1. Use the Ideal Gas Law to calculate the moles of hydrogen.
(4 significant figures + 1 guard digit)
2. Calculate the moles of Na and Ca (This is the tough part).
The balanced equations are
2Na + 2H₂O → 2NaOH + H₂
2Ca + 2H₂O → Ca(OH)₂ + 2H₂
Let mass of Na =
moles of H₂ = moles of H₂ from Na + moles of H₂ from Ca
moles of H₂ from Na =
moles of H₂ from Ca = (2.00 -
(0.049 90 – 0.024 950
moles of H₂ from Na + moles of H₂ from Ca = total moles of H₂
Mass of Na = 1.01 g
3. Calculate the % of Na by mass.
% Na =