A quantity of heat equal to 1.5 kJ was reported to some gas. What mechanical work did

A quantity of heat equal to 1.5 kJ was reported to some gas. What mechanical work did the gas do if the internal energy changed by 900 Joules?

Let’s write down briefly given:

Q = 1.5 kJ (the amount of heat imparted to the gas);

ΔU = 900 J (internal energy).

To find:

A -? (mechanical work of gas).

We will use the first law of thermodynamics for the solution. Let’s remember it:

Q = A + ΔU.

Let’s consider two possible solutions:

a) if ΔU> 0, then we calculate the work by the formula that we remembered above:

Q = A ‘+ ΔU;

A ‘= Q – ΔU = 1500 – 900 = 600 J.

b) provided that the internal energy has decreased then A ‘= 1,500 + 900 = 2,400 J.

Answer: a) 600 J; b) 2,400 J.