Question

27. The value of AE for a system when the surrounding does work (13KJ) on the system and the system gains 9 kJ of heat from the surrounding kJ. A) 22 B) -22 C) -4 D) 4 E) 11

Answer 1

Work done by surrounding = 13kJ

Heat gained by system = 9kJ

As per first law of thermodynamics:
$\Delta E = Q - W$

Here, $\Delta E$ is the change in internal energy of the system, Q is the heat transfer from/into the system and W is net work done by the system. If heat is transferred into the system : Q > 0 , and if work is done by the system : W> 0 .

In this case: Q = +9kJ (heat is being gained by the system)
W = -13kJ (work is being done by the surrounding- on the system)

Therefore, :

$\Delta E = Q - W$
$\Delta E = 9kJ - (-13kJ)$

$\Delta E = 9 kJ + 13 kJ$

$\Delta E = 22 kJ$

Correct answer = option A : 22kJ