Question

How much helium gas would it take to fill a gas balloon with a volume of 11:0 cm3 when the temperature is 41.0◦c and the atmospheric pressure is 790 mm hg? answer in units of mol?

Answer 1

Temperature in Kelvin = 41+273 = 314K
Volume in liter = 11/1000 = 0.011L
Pressure in atmosphere = 790 mmhg = 1atm
Gas constant(R) = 0.082 L-atm-K⁻¹-mol⁻¹
Using ideal gas law equation,
PV=nRT
1×0.011 = n×0.082×314
n = 0.011/0.082×314
n = 4.27×10⁻⁴ moles.
∴ mass of helium gas required = n×4 = 4.27×10⁻⁵×4 = 1.708×10⁻⁴ gram.