Question

An ideal gas is filled in a closed container. $24J$ of heat are added to a gas in a container, and then the gas does $6J$ of work on the walls of the container. Find out the change in internal energy for the gas?

• A. $-30J$
• B. $-18J$
• C. $4J$
• D. $18J$
• E. $30J$

Answer 1

Answer: (D)

$18J$

As heat is added to the system, thus $Q=+24J$

Work is done by gas, thus $W=+6J$

From 1st law of thermodynamics : $Q=\Delta U+W$

$\therefore$ $24=\Delta U+6$ $⟹\Delta U=18J$