Chemistry — Physical Chemistry for the NEET Exam

Common failure modes

These are the patterns that cause most candidates to lose marks on this topic. Recognising them in advance is half the work.

• !Forgetting to convert temperature to Kelvin in all thermodynamic and kinetic equations
• !Misapplying the Nernst equation — forgetting that E = E° − (RT/nF) ln Q, with n = moles of electrons transferred
• !Confusing ΔG and ΔG° — ΔG = ΔG° only at standard conditions; otherwise ΔG = ΔG° + RT ln Q
• !Colligative property errors: misapplying the van't Hoff factor i for electrolytes vs non-electrolytes
• !First-order vs second-order half-life confusion in chemical kinetics

Study tips

• 1Build a Physical Chemistry formula sheet: ΔG = ΔH − TΔS; Kp vs Kc relation; Nernst equation; Arrhenius equation; van't Hoff factor; Raoult's law; first/second-order integrated rate laws.
• 2Drill numericals on elevation of boiling point (ΔTb = Kb × m × i) and depression of freezing point (ΔTf = Kf × m × i). NEET frequently tests these with given Kb/Kf values.
• 3Memorise standard electrode potentials of common half-reactions (Zn²⁺/Zn, Cu²⁺/Cu, Fe³⁺/Fe²⁺) — NEET tests cell EMF calculation from these.
• 4For chemical equilibrium, practise ICE table problems (Initial, Change, Equilibrium) for Kc and Kp calculation.
• 5Solve at least 3 past-year NEET Physical Chemistry questions per day in the final month — the pattern repeats.

Sample NEET Chemistry — Physical Chemistry questions

These sample items mirror the format and difficulty of real NEET questions. Practice with thousands more on the free Koydo question bank.

1. 1

   For a first-order reaction, the half-life is:

   • ADependent on the initial concentration
   • B0.693 / kCorrect
   • C1 / k[A]₀
   • Dk / 0.693
   Why this answer?

   For a first-order reaction, the integrated rate law gives t½ = 0.693/k (where k is the rate constant). This is independent of initial concentration — a characteristic of first-order kinetics. For second-order, t½ = 1/(k[A]₀), which depends on initial concentration.

2. 2

   Spontaneity of a reaction at constant T and P is governed by:

   • AΔH < 0 alone
   • BΔS > 0 alone
   • CΔG < 0Correct
   • DΔH > ΔS
   Why this answer?

   A process is spontaneous at constant temperature and pressure if ΔG < 0, where ΔG = ΔH − TΔS. Neither ΔH < 0 nor ΔS > 0 alone is sufficient. Both ΔH and ΔS contribute to ΔG, and temperature determines which term dominates.

3. 3

   The van't Hoff factor (i) for MgCl₂ (assuming complete dissociation) is:

   • A1
   • B2
   • C3Correct
   • D4
   Why this answer?

   MgCl₂ → Mg²⁺ + 2Cl⁻, producing 3 ions per formula unit. The van't Hoff factor i = 3 for complete dissociation. It is used in colligative property calculations: ΔTb = i × Kb × m.