What is the pressure (in atm) of hydrogen gas in the 20.0 L headspace of a reactor vessel when 2.84 kg sodium is reacted with excess water at 50.0°C?

Question

2 Na(s) + 2 H₂O(l) → 2 NaOH(aq) + H₂(g)

Answer 1

Find moles of hydrogen gas from 2,840g of sodium:

(2,840g Na) * (1 mol Na/ 22.99g Na) * (1 mol H₂ / 2 mol Na) = 61.8 mol H₂.

With the ideal gas law PV = nRT, P = (61.8 mol) (0.08206 L atm/mol K) (50.0 + 273.15K) / (20.0 L) = 81.9 atm.