Question

Heat of 30 kcal is supplied to a system and 4200 J of external work done is done on the system so that its volume decreases at constant pressure what is the change in its internal energy..?

Answer 1

Answer:

Use the formula Delta U=q-w

here as the heat is evolved so q will be negative and as the work is done on the system W will be positive

Delta will be=-30-4200

Delta U will be -4500

Answer 2

Answer:

167.52 kJ.

Explanation:

Since, the law of thermodynamics states the the change in internal energy which is delta U = q+ W where q is the heat released and the W is the work done by or for the system.

So, here q is negative since heat is released and W is positive as work is done on the system. The q will be 30*1000*4.184 = 125520 J. So, the internal energy will be U = -125520 - 42000 = -167520 J = 167.52 kJ.