Multiple Choice
A 1.44-g sample of an unknown pure gas occupies a volume of 0.335 L at a pressure of 1 atm and a temperature of 100.0°C. What is the molar mass of the unknown gas?
7. Gases
The Ideal Gas Law: Molar Mass
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An unknown gas occupies a volume of 1250 mL at 26°C and 705 torr. If the mass is 2.37 g, what is the molar mass of the gas? (R = 0.0821 L·atm/mol·K)
A
18.0 g/mol
B
44.0 g/mol
C
32.0 g/mol
D
28.0 g/mol
Verified step by step guidance1
Convert the given volume from milliliters to liters by dividing by 1000. This is necessary because the ideal gas constant R is given in L·atm/mol·K.
Convert the temperature from degrees Celsius to Kelvin by adding 273.15. This is required because the ideal gas law uses temperature in Kelvin.
Convert the pressure from torr to atm by dividing by 760, as the ideal gas constant R is given in terms of atm.
Use the ideal gas law equation \( PV = nRT \) to solve for the number of moles \( n \). Rearrange the equation to \( n = \frac{PV}{RT} \). Substitute the converted values for pressure, volume, and temperature, along with the given R value.
Calculate the molar mass of the gas by dividing the mass of the gas by the number of moles calculated in the previous step. Use the formula \( \text{Molar Mass} = \frac{\text{mass}}{n} \).
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