A 226.4-l cylinder contains 65.5% he (g) and 34.5% kr (g) by mass at 27.0°c and 1.40 atm total pressure. what is the mass of he in this container?

First, we determine the number of moles of gas present using the ideal gas equation.

PV = nRT

n = PV / RT

n = (1.4 * 226.4) / (0.082 * (27 + 273.15))

n = 12.88

Next, we use the given percentages to find the moles of helium present

Moles of helium = 0.655 * 12.88

Moles of helium = 8.44

Next, we use the formula:

Mass = moles * molar mass

Mass of helium = 8.44 * 4

Mass of helium = 33.76 grams