Question

#1: The following question appears on a quiz: "A 1.0 L balloon has a pressure of 153 kPa at a temperature of 60°C. How many moles of gas are inside the balloon?" A student answers 0.31 moles. Which of the following explanations is true?

A. The student used the wrong value for R, and the answer should be 5.60 moles.

B. The student used the wrong temperature units, and the correct answer should be 0.06 moles.

C. The student's answer is correct.

D. The student used the wrong volume, and the answer should be 5.60 moles.

Answer 1

Option B.The student used the wrong temperature units, and the correct answer should be 0.06 moles.

Use the ideal gas equation: pV = nRT

V= 1.0L
p = 153 kPa
T = 60 °C + 273.15 = 333.15 K
n = ?

n = [pV] / [RT]

R = 0.082 atm*L / K*mole

n = [153 kPa * 1atm / 101.325 Kpa *1.0L] / [0.082 atm*L / K*mole * 333.15 k] =

n = 0.06 mole

If you incorrectly use T = 60, the result is 0.31mole.

The error is to use T in celsius. T must be used in Kelvin.