JEE Main 2017 · 9 Apr · Shift 1 · Chemistry Q31

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ChemistrySingle correct+4 / -1Question 31 of 90

An ideal gas undergoes isothermal expansion at constant pressure. During the process :

enthalpy increases but entropy decreases.

enthalpy remains constant but entropy increases.

enthalpy decreases but entropy increases.

Both enthalpy and entropy remain constant.

Answer and worked solution

Official answer: B

For an ideal gas H depends only on T, so it stays constant in an isothermal process. The volume grows, so the entropy increases ( $\Delta S=nR\ln\frac{V_2}{V_1}>0$ ).

Topics:Entropy First law and enthalpy

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JEE Main 2017 · 9 Apr · Shift 1, Chemistry question 31