Question

Calculate ΔE for a system that absorbs 521.0 kJ of heat from its surroundings and does 316.0 kJ of work on its surroundings. Answer should be in kj.

Answer 1

Solution

Mathematical statement of first law of Thermodynamics is given as,

i.e

change in internal energy is due to heat supplied to the system and work done on the system

now

when heat is absorbed by the system it is +ve ( q = +521 KJ)

when work is done on the system it is +ve ( during compression)

when work is done on the surrounding it is -ve

here work is done on the surrounding hence -ve ( W = -316 KJ )

therefore

521.0 kj +(-316kj)

          = 521-316 kj

          205 KJ