What volume of hydrogen is formed when interacting with 0.5 liters of water 20 g of calcium containing 5% impurities?

| December 9, 2020 | education

What volume of hydrogen is formed when interacting with 0.5 liters of water 20 g of calcium containing 5% impurities? Calculate the mass fraction of alkali in the resulting solution.

1) w (Ca without impurities) = 100% -w (impurities)
w (pure Ca) = 100% -5% = 95%
2) m (Ca) = m (solution) * w
m (Ca) = 20 * 0.95 = 19 (g)
Ca + 2H2O = Ca (OH) 2 + H2
3) n (Ca) = m (Ca) / M
M (Ca) = 40 (g / mol)
n (Ca) = 19/40 = 0.475 (mol)
4) n (Ca) = n (Ca (OH) 2 = 0.475 mol
M (Ca (OH) 2 = 40 + 34 = 74 (g / mol)
m (Ca (OH) 2 = 0.475 * 74 = 35.15 (g)
5) n (Ca) = n (H2) = 0.475 mol
V (H2) = 22.4 * 0.475 = 10.64L
m (H2) = 0.475 * 2 = 0.85 (g)
6) m (H20) = 0.5 * 1 = 500 (g)
7) m (solution) = 500 + 20-0.95 = 519.05 (g)
8) m (Ca (OH) 2 = 35.5 / 519.05 = 6.8%
Answer: 6.8%, 10.64L



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