Question

typical room is 4.0 m long, 5.0 m wide, and 2.5 m high. What is the total mass of the oxygen in the room assuming that the gas in the room is at STP and that air contains 21% oxygen and 79% nitrogen?

Answer 1

mass of oxygen gas in Kg = 15.0Kg

Step-by-step explanation:

Volume of air in the room = 4.0m*5.0m*2.5m = 50m³

volume of oxygen in the room = 21/100 * 50m³ = 10.5m³

using the ideal gas equation; PV=nRT

number of moles of oxygen gas, n = PV/RT

At STP, P = 1atm, V = 10.5m³ = (10.5*1000)dm³ = 10500dm³, R = 0.082 atmdm³K⁻¹mol⁻¹, T = 273K

n = 1 * 10500/ (273 *0.082)

n = 469.04 moles

mass of oxygen gas in Kg = (no of moles * molar mass)/1000

molar mass of oxygen gas = 32g

mass of oxygen gas in Kg = (469.04 * 32)/1000

mass of oxygen gas in Kg = 15.0Kg