Compression changes the sign of the logarithm

A fixed amount of ideal gas is compressed reversibly at constant temperature from 6 L to 2 L. Its constant nRT equals 150 J.

What is the heat Q into the gas?

Organize the givens & assumptions

Vi = 6 L
Vf = 2 L
nRT = 150 J

Closed fixed amount of ideal gas, constant stated heat capacities, negligible bulk kinetic and gravitational energy changes, and only pressure–volume work. Heat into the gas and work by the gas are positive.

A $-100\ \mathrm J$
B $-150\ln3\ \mathrm J$
C $150\ln3\ \mathrm J$
D $0\ \mathrm J$

Try it on paper first. Free sample problems in every collection include the complete reasoning: find one in this collection →