Question

A system receives 425 J of heat and delivers 425 J of work to its sorroundings. what is the change in internal energy of the system?

Answer 1

According to first law of thermodynamics we know that du = dq + dw ;

du = change in internal energy

dq = heat change that is heat absorbed by the system taken as +ve and heat released by the system taken as -ve ( IUPAC convention)

dw = work done by the system taken as -ve and work done on the system taken as +ve

Here system absorb heat from the surroundings so it will be +ve and work done by the system so it will be -ve.

So du = +425 + (-425) = 0

So change in internal energy is zero (ans)