Multiple Choice
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?
7. Gases
The Ideal Gas Law: Molar Mass
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What is the mass (in grams) of 10.00 L of propane vapor (C₃H₈) at STP?
A
10.0 grams
B
44.1 grams
C
19.6 grams
D
22.4 grams
Verified step by step guidance1
Identify the conditions of STP (Standard Temperature and Pressure), which are 0°C (273.15 K) and 1 atm pressure. At STP, 1 mole of any ideal gas occupies 22.4 L.
Determine the molar volume of propane (C₃H₈) at STP. Since 1 mole of gas occupies 22.4 L, calculate how many moles are in 10.00 L of propane using the formula: \( \text{moles of C₃H₈} = \frac{10.00 \text{ L}}{22.4 \text{ L/mol}} \).
Calculate the molar mass of propane (C₃H₈). The molar mass is the sum of the atomic masses of all the atoms in the molecule: \( 3 \times \text{atomic mass of C} + 8 \times \text{atomic mass of H} \).
Use the number of moles calculated in step 2 and the molar mass from step 3 to find the mass of propane. Use the formula: \( \text{mass} = \text{moles} \times \text{molar mass} \).
Verify the units and ensure that the final answer is in grams. This will give you the mass of 10.00 L of propane at STP.
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