Question

A system absorbs 50J of heat during a transformation. Determine the change in internal energy if 

the system perform, (a) 15J and (b) 65J of work on the surrounding.

Find the ∆E

a) When 175J of work is done on a system that evolves 50J of heat to the surrounding.

b) When a gas absorbs 28kJ of heat and 13kJ of work done on it.

Answer 1

a. W=-15J

q=50

$\Delta U=q+W=50-15=45 J$

W=-65

$\Delta U=q+W=50-65=-15 J$

a) q=-50

W=175

$\Delta U=q+W=-50+175=125 J$

b) q=28000

W=13000

$\Delta U=q+W=28000+13000=41000 J$