Calculate the amount of gas produced when collected by water displacement.

Question

Oxygen gas can be prepared by heating potassium chlorate:

2KClO₃(s)2KCl(s) + 3O₂(g)

In one experiment, a sample of KClO₃ reacts and the gas produced is collected by water displacement. The gas sample has a temperature of 21.00 °C, a volume of 890.0 mL, and a pressure of 752.0 mm Hg. Calculate the amount (in moles) of oxygen gas produced in the reaction. The vapor pressure of water is 18.65 mm Hg at 21.00 °C.

______ mol

Answer 1

2KClO₃(s) ==> 2KCl(s) + 3O₂(g) ... balanced equation

Use the ideal gas law to find the moles of O₂ gas

PV = nRT

P = pressure of O2 = total pressure - pressure of water vapor = 752.0 mm - 18.65 mm = 733.35 mm Hg

V = volume in liters = 0.7520 L

n = moles

R = gas constant = 62.36 LmmHg / Kmol

T = temp in Kelvin = 21.00 + 273.15 = 294.15)

Solving for n, we have

n = PV/RT = (733.35 mm Hg)(0.752 L) / (62.36 LmmHg/Kmol)(294.15K)

n = 0.03006 moles