Question

Assertion: For an isothermal reversible process $Q=-W$ i.e. work done by the system equals the heat absorbed by the system.
Reason : Enthalpy change $(\Delta H)$ is zero for isothermal process.

• A. If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
• B. If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
• C. If the Assertion is correct but Reason is incorrect.
• D. If the Assertion is incorrect and Reason is correct.

Answer 1

Answer: (B)

In an isothermal process change in internal energy $(\Delta E)$ is zero (as it is a function of temperature).
$\therefore$ According to first law of thermodynamics
$\because Q+W=\Delta E$. Hence $Q=-W($ if $\Delta E=0)$
If a system undergoes a change in which internal energy of the system remains constant (i.e. $\Delta E=0$ ) then $-W=Q$. This means that work done by the system equals the heat