Question

For a particular reaction, the system absorbs 8 kJ of heat and does 2.5 kJ of work on its surrounding. What will be the change in internal energy of the system?

Options

• −10.5 kJ

• −5.5 kJ

• +5.5 kJ

• +10.5 kJ

Answer 1

+5.5 kJ

Explanation:

According to the 1^st Law of thermodynamics,

ΔU = Q + W

Q = 8 kJ, W = −2.5 kJ

∴ ΔU = 8 kJ − 2.5 kJ

= +5.5 kJ

Internal energy of the system increases by +5.5 kJ.