Molar Heat Capacities: an Ideal Monatomic Gas Cools from 455

Multiple Choice

Molar heat capacities: An ideal monatomic gas cools from 455.0 K to 405.0 K at constant volume as 831 J of energy is removed from it. How many moles of gas are in the sample? The ideal gas constant is R = 8.314 J/mol ∙ K.

A) 2.50 mol
B) 2.15 mol
C) 1.50 mol
D) 1.33 mol
E) 0.725 mol