Answer: 20.7 kJ
Explanation:
According to first law of thermodynamics:
[tex]\Delta E=q+w[/tex]
[tex]\Delta E[/tex]=Change in internal energy
q = heat absorbed or released
w = work done or by the system
w = work done on the system=[tex]-P\Delta V[/tex] {Work is done on the system is positive as the final volume is lesser than initial volume}
w = 4.51 kcal = [tex]4.51\times 4.184kJ=18.9kJ[/tex] (1kcal = 4.184kJ)
q = +1.79 kJ {Heat absorbed by the system is positive}
[tex]\Delta E=+1.79+(18.9)=20.7kJ[/tex]
Thus [tex]\Delta E[/tex] for a system that receives 1.79 kJ of heat from surroundings and has 4.51 kcal of work done on it at the same time is 20.7 kJ
