0.300 mol of an ideal gas is initially at a volume of 2.00L. It expands against a constant external pressure of 120 kPa to reach the final volume o 2.30L.

Question

0.300 mol of an ideal gas is initially at a volume of 2.00L. It expands against a constant external pressure of 120 kPa to reach the final volume o 2.30L. In the process it absorbs 24.3 J of heat. Calculate the change in internal energy of the gas.

Answer 1

ΔU = q + w

ΔU = change in internal energy = ?

q = heat = + 24.3 J (+ because heat is absorbed)

w = work = -PΔV = -pressure x change in volume

w = -120kPa x1 atm/101.325 kPa x 0.30 L

w = -0.355 L-atm x 101.325 J/Latm = -36 J (- because work is done by the system)

ΔU = q + w = 24.3 J - 36 J = -11.7 J

please be sure to check the math.

please note I changed kPa to atm and then changed Latm to joules.