A system absorbs 21.6 kJ of heat while performing 6.9 kJ of work on the surroundings. If the initial internal energy, E, is 61.2 kJ, what is the final value of E?

Final Energy is 75.9 kJ

Explanation:

Given:

Heat absorbed, Q = 21.6 kJ

Work done by the system on the surrounding, W = - 6.9 kJ

Initial internal energy of the system, Ei = 61.2 kJ

From the first law of thermodynamics, we have

Change in energy = Heat absorbed + Work done

or

Final energy (Ef) - Initial energy (Ei) = Q + W

on substituting the values in the above formula, we get

Ef - 61.2 kJ = 21.6 kJ + ( - 6.9 kJ)

or

Ef = 14.7 kJ + 61.2 kJ

or

Ef = 75.9 kJ

Hence, the final Energy is 75.9 kJ