Question

Calculate the change in internal energy of the system if 25 kJ of work is done by the system and it absorbs 10 kJ of heat.

• A. -10 kJ
• B. -35 kJ
• C. -15 kJ
• D. -25 kJ

Hint:

The change in internal energy can be calculated using the first law of thermodynamics: \( \Delta U = Q - W \), where \( Q \) is heat absorbed and \( W \) is work done.

Answer 1

The Correct Option is D

Step 1: Apply the first law of thermodynamics.
The first law of thermodynamics is given by:
\[ \Delta U = Q - W \]
where:
- \( \Delta U \) is the change in internal energy,
- \( Q \) is the heat absorbed by the system,
- \( W \) is the work done by the system.

Step 2: Substitute the given values.
We are given that:
- The system absorbs 10 kJ of heat, so \( Q = 10 \, \text{kJ} \),
- The system does 25 kJ of work, so \( W = 25 \, \text{kJ} \).
Using the first law of thermodynamics, we have: \[ \Delta U = 10 - 25 = -15 \, \text{kJ} \]

Step 3: Final conclusion.
Thus, the change in internal energy of the system is:
\[ \boxed{-25 \, \text{kJ}} \]