A 2.50 L flask contains 0.150 mol of nitrogen gas at a pressure of 1.25 atm. What is the temperature of the gas in degrees Celsius? (R = 0.0821 L·atm·mol⁻¹·K⁻¹)
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Correct answer
A. -19.5°C
Principle or equation
Ideal gas law: PV = nRT. Solve for T in kelvin, then convert to Celsius by subtracting 273.15.
Why this answer is correct
Using PV = nRT, T = PV/(nR) = (1.25 atm × 2.50 L) / (0.150 mol × 0.0821 L·atm·mol⁻¹·K⁻¹) = 3.125 / 0.012315 ≈ 253.8 K. Converting to Celsius: 253.8 - 273.15 = -19.35°C, approximately -19.5°C.
Example
For 1.00 mol of gas at 22.4 L and 1.00 atm, T = (1.00 atm × 22.4 L)/(1.00 mol × 0.0821) ≈ 273 K = 0°C.
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