Since one mole of HCl occupies 12 L at this temperature and pressure, 3 L HCl then
corresponds to 0.25 mol. Since 2 mol of HCl are produced from each mol of Cl 2 , 0.25 mol HCl
would be produced from 0.125 mol of Cl 2 . The molecular weight of Cl 2 is 71, so the answer is
(71 g/mol of Cl 2 ) (0.125 mol) = 8.88 g.9 . 38 torr, 152 torr, 152 torr, 38 torrAccording to Dalton’s law of partial pressures, the sum of the partial pressures of the gases in a
mixture is equal to the total pressure of the mixture. Therefore, the partial pressures of
nitrogen, oxygen, helium, and chlorine will add up to 380 torr. The partial pressure of a gas A,
PA, is calculated using the equation PA = PT XA where X is the mole fraction of the gas A and PT is
the total pressure. First, then, one must calculate the number of moles of each gas present by
dividing the mass of each gas by its molar mass, and then determine the mole fraction of each.
It can be easily verified that XN 2 = 0.1, XO 2 = 0.4, XHe = 0.4, and XCl 2 = 0.1. Now the partial pressures
may be calculated:10 . E
The average kinetic energy of a gas is proportional to its temperature in K, not °C.11 . 0.4
Rearranging the equation: