# When an excess of sodium hydroxide solution interacts with 16 g of silicon, 22.4 liters of hydrogen were obtained

When an excess of sodium hydroxide solution interacts with 16 g of silicon, 22.4 liters of hydrogen were obtained, calculate the mass fraction of silicon in the sample taken.

Given:
m tech. (Si) = 16 g
V (H2) = 22.4 L

Find:
ω (Si) -?

1) Write the reaction equation:
2NaOH + Si + H2O => Na2SiO3 + 2H2 ↑;
2) Calculate the amount of substance H2:
n (H2) = V (H2) / Vm = 22.4 / 22.4 = 1 mol;
3) Determine the amount of substance Si:
n clean (Si) = n (H2) / 2 = 1/2 = 0.5 mol;
4) Calculate the mass of pure Si:
m clean (Si) = n pure. (Si) * M (Si) = 0.5 * 28 = 14 g;
5) Calculate the mass fraction of Si:
ω (Si) = m pure. (Si) * 100% / m tech. (Si) = 14 * 100% / 16 = 87.5%.

Answer: The mass fraction of Si is 87.5%.

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