Question

Calculate the change internal energy (?E) for a system that is giving off 45.0 kJ of heat and is performing 855 J of work on the surroundings.(pay attention to units!)A. 9.00 x 102 kJB. -9.00 x 102 kJC. �44.1 kJD. �45.9 kJE. 44.1 kJ

Answer 1

D. - 45.9 kJ

Step-by-step explanation:

According to the first law of thermodynamics:-

`\Delta U = q + w`

Where,

U is the internal energy

q is the heat

w is the work done

From the question,

q = - 45.0 kJ = - 45000 J ( 1 kJ = 1000 J ) (+ sign as the heat is being released)

w = 855 J (work is done on the surroundings)

So, work done by the system = - 855 J

So,

`\Delta U = -45000\ J-855\ J = -45855\ J= -45.9\ kJ`