Question

in a thermodynamic process an ideal gas absorbs 20 J of heat and does 25 J of work.if initial internal energy of the gas is 60J then the final internal energy will be?a)65J b)55J c)105J d)15J​

Answer 1

$\boxed{\bold {\green{Answer}}}$

Final internal energy = 55J

$\boxed{\bold {\green{Explanation}}}$

Given:

• ΔQ(heat) = +20J
• ΔW(work) = +25J
• $U_i = 60J$

To Find:

Final internal energy(U final) of the system

Solution:

w.k.t

$\boxed{\bold {\pink{ΔQ = ΔU + ΔW}}}$

$\mathsf{ΔQ= U_f - U_i + ΔW}$

$\mathsf{20J = U_f - 60J + 25J}$

$\mathsf{20J = U_f - 35 J}$

$\mathsf{U_f = 55 J}$

Final internal energy = 55J

Note:

•If heat is absorbed by the system then Q is +ve

• If heat is taken from the system, then

Q is -ve

• If work is done by the system, then

W is +ve

•If work is done on the system, then

W is -ve