What is the mass in grams of 250 ml of PH3 at STP?

We can find the number of moles of PH₃ using ideal gas law equation

PV = nRTwhere

P - standard pressure - 101 325 Pa

V - volume - 250 x 10⁻⁶ m³

n - number of moles

R - universal gas constant - 8.314 Jmol⁻¹K⁻¹

T - temperature - 273 K

substituting the values in the equation

101 325 Pa x 250 x 10⁻⁶ m³ = n x 8.314 Jmol⁻¹K⁻¹ x 273 K

n = 0.011 mol

therefore mass of PH₃ = 0.011 mol x 34 g/mol = 0.374 g

mass of PH₃ is 0.374 g