Calculate the volume of hydrogen that will evolve during the interaction of sodium weighing

Calculate the volume of hydrogen that will evolve during the interaction of sodium weighing 11.5 grams, mass fraction of impurities 10%, with water.

Given:
m mixture (Na) = 11.5 g
w approx (Na) = 10%
To find:
V (H2)
Decision:
2Na + 2H2O = 2NaOH + H2
w is clean. islands (Na) = 100% -10% = 90% = 0.9
m in-va (Na) = w * m mixture = 0.9 * 11.5 g = 10.35 g
n (Na) = m / M = 10.35 g / 23 g / mol = 0.45 mol
n (Na): n (H2) = 2: 1
n (H2) = 0.45 mol / 2 = 0.225 mol
V (H2) = n * Vm = 0.225 mol * 22.4 L / mol = 5.04 L
Answer: 5.04 L