What is the density of sulfur dioxide gas at 90.0 kPa and 45°C?

Question

(Answer: 2.18 g/L)

Can someone explain how to do this problem please?

Answer 1

Sometimes, when given this type of question, it is easiest to assume that you have 1 liter volume. Then we can use the ideal gas law, PV = nRT and solve for moles and then convert to grams.

P = pressure = 90.0 kPa x 1 atm/101.325 kPa = 0.888 atm (converted to atm so can use R = 0.0821)

V = volume = 1 L

n = moles = ?

R = gas constant = 0.0821 Latm/Kmol

T = temp in K = 45 + 273 = 318K

Solving for n (moles) we have...

n = PV/RT = (0.888)(1)/(0.0821)(318)

n = 0.034 moles SO₂

molar mass SO2 = 32 + 32 = 64 g/mol

Grams SO2 present = 0.034 mol x 64 g/mol = 2.18 g

Since we have a volume of 1 liter, the density will be 2.18 g/L