Multiple Choice
What mass of helium gas is present in a 14.5 L sample at 273 K and 1 atm, assuming ideal gas behavior? Express your answer in grams.
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7. Gases
The Ideal Gas Law: Molar Mass
Multiple Choice
A 1.00 L sample of a gas has a mass of 1.25 g at STP. What is the mass of 1.00 mol of this gas?
A
12.5 g
B
1.25 g
C
28.0 g
D
22.4 g
Verified step by step guidance1
Identify the given information: volume of the gas sample \(V = 1.00\ \text{L}\), mass of the gas sample \(m = 1.25\ \text{g}\), and the conditions are at STP (Standard Temperature and Pressure).
Recall that at STP, 1 mole of any ideal gas occupies a volume of 22.4 L. This is a key relationship to connect volume and moles for gases under these conditions.
Calculate the number of moles in the 1.00 L gas sample using the molar volume at STP: \(n = \frac{V}{22.4\ \text{L/mol}}\).
Determine the molar mass (mass per mole) of the gas by dividing the mass of the sample by the number of moles calculated: \(M = \frac{m}{n}\).
Use the molar mass to find the mass of 1.00 mole of the gas, which is the value of \(M\) obtained in the previous step.
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