A1.50 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?

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 = (82.0575 atm.cm^3/mol.K)( 298.15 K)/1.50 x 10^3 cm^3) x (0.158 mole + 0.09 mol + 0.044 mol) = 4.76 atm

The answer is c) pyrite