Multiple Choice
A 0.465 g sample of an unknown compound occupies 245 mL at 298 K and 1.24 bar. What is the molar mass of the unknown compound?
7. Gases
The Ideal Gas Law: Molar Mass
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A sample of gas has a mass of 0.565 g. Its volume is 116 mL at a temperature of 87 °C and a pressure of 781 mmHg. Using the Ideal Gas Law, what is the molar mass of the gas?
A
28.0 g/mol
B
44.0 g/mol
C
32.0 g/mol
D
18.0 g/mol
Verified step by step guidance1
Convert the temperature from Celsius to Kelvin by adding 273.15 to the Celsius temperature: T(K) = 87 + 273.15.
Convert the volume from milliliters to liters by dividing by 1000: V(L) = 116 / 1000.
Convert the pressure from mmHg to atm using the conversion factor 1 atm = 760 mmHg: P(atm) = 781 / 760.
Use the Ideal Gas Law equation, PV = nRT, to solve for the number of moles (n). Rearrange the equation to n = PV / RT, where R is the ideal gas constant (0.0821 L·atm/mol·K).
Calculate the molar mass of the gas by dividing the mass of the gas by the number of moles: Molar Mass = mass / n.
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