An ideal gas (the system) is contained in a flexible balloon at a pressure of 1 atm and is initially at a temperature of 20.°C. The surrounding air is at the same pressure, but its temperature is 25°C. When the system has equilibrated with its surroundings, both system and surroundings are at 25°C and 1 atm. In changing from the initial to the final state, which one of the following relationships regarding the system is correct?

(A) ΔE <0

(B) ΔE=0

(C) ΔH=0

(D) w>0 q>0

Answer: (E) q>0

Explanation:

∆U = q-w

Since there is no expansion or compression work = w = 0

Therefore, ∆U = q, which means option A, B, D is incorrect.

∆H = ∆U + P∆V

Where P∆V=0

That' gives ∆H=∆U, making option C incorrect.

The answer is E) q>0 because temperature of system is increased.

Explanation: As a result of the surrounding heat giving out heat to the system (Endothermic reaction), {q>0 positive}

This positive sign 'q' tells us that heat is absorbed by the system, that is to say the temperature of the system increases.

Since the energy goes to the system, it means the final heat energy is greater than the initial energy.

Delta Q = final Q - Initial Q is positive because of the energy influx.