A one mole sample of an ideal gas performs 374J of work and

A one mole sample of an ideal gas performs 37.4J of work and absorbs 12.4J of heat. Calculate the internal energy of the gas.

Solution

we know that

dU = q + w

given

12.4 J of heat is absorbed and heat absorbed is positive

so

q = 12.4 J

now

work done by the gas is negative

so

w = -37.4 J

so

dU = q + w

dU = 12.4 - 37.4 J

dU = -25 J

so

change in internal energy is -25 J