Chemical kinetics is the branch of physical chemistry that studies the speed (rate) of chemical reactions and the factors that influence them. It answers two fundamental questions: (1) How fast does a reaction proceed? (2) What factors control this speed?

Key Scope of Chemical Kinetics

• Measuring reaction rates
• Determining rate laws (rate expressions)
• Understanding reaction mechanisms (step-by-step pathways)
• Predicting how changes in conditions affect rate
• Applying to industrial processes, pharmaceutical development, and environmental chemistry

What Kinetics Does NOT Tell Us

Kinetics does not predict the direction of a reaction (that is thermodynamics — $\Delta G$). A thermodynamically favorable reaction (negative $\Delta G$) can still be kinetically slow (e.g., diamond → graphite is thermodynamically favorable but kinetically negligible at room temperature).

Relationship to Equilibrium

Kinetics and equilibrium are related: at equilibrium, the forward and backward rates are equal. The ratio of forward to backward rate constants (k_fwd/k_rev) equals the equilibrium constant K. However, a large K does not mean a fast reaction.

NEET Relevance

Chemical kinetics appears in 2–3 questions per year. Focus areas: rate law determination, integrated equations, half-life calculations, and Arrhenius equation problems.