🧪 Chemistry · Thermodynamics · NEET & JEE

Given ΔHf(CO2) = −393.5 and ΔHf(CO) = −110.5 kJ/mol, the enthalpy change for CO(g) + ½O2(g) → CO2(g) is:

Answer: −283 kJ.

A −504 kJ
B −283 kJ
C +283 kJ
D −110 kJ

Correct answer: B. −283 kJ

Explanation: ΔH = ΔHf(CO2) − ΔHf(CO) = −393.5 − (−110.5) = −283 kJ.

Isothermal expansion follows a gentler curve (heat flows in to keep T constant) while adiabatic expansion drops in pressure more steeply (no heat exchange, so internal energy and temperature fall as the gas does work).

Concept context

Study energy changes in chemical reactions. Understand enthalpy, entropy, Gibbs free energy, and the laws of thermodynamics that decide whether a reaction will occur spontaneously or not.

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Given ΔHf(CO<sub>2</sub>) = −393.5 and ΔHf(CO) = −110.5 kJ/mol, the enthalpy change for CO(g) + ½O<sub>2</sub>(g) → CO<sub>2</sub>(g) is:

Concept context

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