Question

A 1.50 liter flask at a temperature of 25°C contains a mixture of 0.158 moles of methane, 0.09 moles of ethane, and 0.044 moles of butane. What is the total pressure of the mixture inside the flask?

Answer 1

This can be solved using Dalton's Law of Partial pressures. This law states that the total pressure exerted by a gas mixture is equal to the sum of the partial pressure of each gas in the mixture as if it exist alone in a container. In order to solve, we need the partial pressures of the gases given. Calculations are as follows:

P = P1 + P2 + P3
P = (0.08206 atm.L/mol.K)( 298.15 K)/1.50) x (0.158 mole + 0.09 mol + 0.044 mol) = 4.76 atm

Answer 2

To answer this question, we use the ideal gas equation PV=nRT where P is pressure, V is volume, n is the number of moles, R is the gas constant and T is temperature. We add first the number of moles, that is a total of 0.292 moles. Using PV=nRT, the answer is 4.76 atm.