# Chemistry-Gases, dalton's law?????

A vessel contains 2.00 mol of He, 5.50 mol of Ar, and 1.00 mol of CH4 gases. If the partial pressure of He is 1.440 atm, what is the total pressure inside the vessel?

Relevance

Partial pressure = total pressure x mole fraction

mole fraction = moles of the gas/total moles of all gases

You know the partial pressure of He and you know the mole fraction (2.00 moles He out of 8.50 moles total). Solve for total pressure

1.440 = P(2/8.50)

P = (1.440)(8.50)/2

P = 6.12 atm

Dalton's law of partial pressures simply states that the total gas pressure in a container or a system is equal the the partial pressures of each component gas. In this problem you have been given the amount of each component gas in moles, and the pressure of the Helium component. Assuming identical conditions for all of the gases in the mixture, since they are all in the same container, you can simply use ratios to solve the problem. The helium is 2/1.44 and should be equal to argon which is 5.50/X. When you solve this inequality, you get 3.96atm. The equality of 2/1.44 = 1/X gives a partial pressure to methane (CH4) of .72 When you add 1.44 + 3.96 + .72 = 6.12 atm of pressure. Hope this helps

2.00 mol He + 5.50 mol Ar + 1.00 mol CH4 = 8.50 mol gases. He = 2.00/8.50 x 100% = 23.5-mol%. The partial pressure of He is 1.44 atm (to three significant figures). The mol% of the rest of the gases is 76.5%. So the total pressure is 6.12atm.

What I don't understand is your evocation of Dalton's law?????