Question

a) A sample of oxygen gas is collected by displacement of water at 25°C and 1.13 atm total pressure. If the vapor pressure of water is 23.756 mm Hg at 25°C, what is the partial pressure of the oxygen gas in the sample?

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b) Calcium oxide can be used to "scrub" carbon dioxide from air.

CaO(s) + CO2(g) → CaCO3(s)

What mass of CO2 could be absorbed by 1.38 g of CaO?

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What volume would this CO2 occupy at STP?

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c) If water is added to magnesium nitride, ammonia gas is produced when the mixture is heated.

Mg3N2(s) + 3 H2O(l)→ 3 MgO(s) + 2 NH3(g)

If 12.7 g of magnesium nitride is treated with water, what volume of ammonia gas would be collected at 21°C and 739 mm Hg?

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Answer 1

a) The partial pressure of oxygen in the sample = 1.13*760 mm Hg - 23.756 mm Hg = 835.044 mm Hg

b) Mass of CO2 that could be absorbed by 1.38 g CaO = {1.38 g/(56 g/mol)}*44 g/mol = 1.084 g

c) Volume of ammonia gas collected = nRT/P = (2*12.7/100)*(0.0821 L.atm/mol.K)*(21+273) K/(739/760) atm = 6.305 L