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🧪 Chemistry  ·  Thermodynamics  ·  NEET & JEE

For a reaction with ΔH = -200 kJ and ΔS = +100 J/K at 300 K, ΔG is:

Answer: -230 kJ.

  • A -170 kJ
  • B -230 kJ
  • C +170 kJ
  • D +230 kJ

Correct answer: B. -230 kJ

Explanation: ΔG = ΔH - TΔS = -200,000 - (300 × 100) = -230,000 J = -230 kJ.

P-V Diagram: Isothermal vs Adiabatic ExpansionVPIsothermal (T constant)Adiabatic (q=0)Adiabatic curve is steeper: no heat enters to cushion the pressure drop

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.

Read the full Thermodynamics notes →