Question #203789

A sample of gas has a mass of 38.7 mg. Its volume is 220 mL at a temperature of 54 ∘C and a pressure of 897 torr. Find the molar mass of the gas. Express your answer in grams per mole to three significant figures.

Expert's answer

m=38.7 mg="38.7 \\times 10^{-3} \\;g"

V=220 mL= 0.22 L

T = 54 + 273 = 327 K

p = 897 torr = 1.18 atm

Ideal Gas Law

pV = nRT

R= 0.08206 L×atm/mol×K

"n= \\frac{pV}{RT} \\\\\n\n= \\frac{1.18 \\times 0.22}{0.08206 \\times 327} \\\\\n\n= 0.00967 \\;mol"

Molar mass "= \\frac{m}{n}= \\frac{38.7 \\times 10^{-3}}{0.00967}=4.00 \\;g\/mol"

Answer: 4.00 g/mol

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