first we need to find the number of HF moles in the sample using the ideal gas law equation
PV = nRT
P - pressure - 2.0 atm x 101 325 Pa/atm = 202 650 Pa
V - volume - 4.50 x 10⁻³ m³
n - number of moles
R - universal gas constant - 8.314 Jmol⁻¹K⁻¹
T - temperature - 300 K
substituting these values in the equation
202 650 Pa x 4.50 x 10⁻³ m³ = n x 8.314 Jmol⁻¹K⁻¹ x 300 K
n = 0.366 mol
molar mass of HF = 20 g/mol
mass present - number of moles x molar mass = 0.366 mol x 20 g/mol = 7.32 g
answer is 1) 7.3 g
