The change in internal energy of a thermodynamical system which has absorbed 2 kcal of heat and done 400 J of work is (1 cal = 4.2 J)

Calculation:

The change in internal energy (ΔU) of a thermodynamical system can be calculated using the first law of thermodynamics:

ΔU = Q - W

Where:

ΔU is the change in internal energy

Q is the heat absorbed by the system

W is the work done by the system

Given:

Heat absorbed, Q = 2 kcal = 2 × 4.2 × 10³ J = 8400 J

Work done, W = 400 J

Now, applying the values in the equation:

ΔU = 8400 J - 400 J = 8000 J = 8 kJ

Thus, the change in internal energy is 8 kJ.