GRE Subject Test: Chemistry

A comprehensive overview of the GRE Subject Test in Chemistry, covering key concepts, problem-solving techniques, and test strategies.

Atomic Structure and PeriodicityChemical Bonding and Molecular StructureStoichiometry and Chemical Calculations
Thermodynamics and Chemical EquilibriumKinetics and Reaction MechanismsSpectroscopy and Analytical Chemistry
Chemistry in HealthcareGreen Chemistry and SustainabilityMaterials Science and Everyday Technology
Time Management and PacingAnswer Elimination and Intelligent Guessing
Atomic Structure and...Chemical Bonding and...Stoichiometry and Ch...Thermodynamics and C...Kinetics and Reactio...Spectroscopy and Ana...Chemistry in Healthc...Green Chemistry and ...Materials Science an...Time Management and ...Answer Elimination a...
Advanced Topics

Thermodynamics and Chemical Equilibrium

Energy, Entropy, and Predicting Reactions

Thermodynamics explains how and why chemical reactions occur. Key concepts include enthalpy (\( \Delta H \)), entropy (\( \Delta S \)), and Gibbs free energy (\( \Delta G \)). Chemical equilibrium occurs when the forward and reverse reaction rates are equal, and concentrations remain constant.

Fundamental Equations

  • Gibbs Free Energy: \( \Delta G = \Delta H - T\Delta S \)
  • Equilibrium constant: \( K = \frac{[products]}{[reactants]} \) at equilibrium

Applications

Predicting if a reaction is spontaneous and understanding how changing temperature, pressure, or concentration shifts equilibrium (Le Chatelier’s Principle) are frequently tested skills.

Impact

These principles guide everything from industrial synthesis of chemicals to how our bodies maintain homeostasis.

Key Formula

\[\Delta G = \Delta H - T\Delta S\]

Examples

  • Predicting if dissolving ammonium nitrate in water is spontaneous at room temperature.

  • Explaining why increasing pressure favors ammonia production in the Haber process.

In a Nutshell

Thermodynamics and equilibrium help chemists predict and control reactions.

Key Terms

Enthalpy
A measure of heat content in a system at constant pressure.
Entropy
A measure of disorder or randomness in a system.
Le Chatelier’s Principle
A system at equilibrium responds to disturbances by minimizing the change.
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Kinetics and Reaction Mechanisms