High-Yield Topics (spend 60% of revision time)

1. Ideal Gas Equation Numericals. Every NEET paper has at least one. Always: convert T to Kelvin, choose correct R, convert mass to moles. Practice until these three steps are automatic. Common forms: find V given P, T, n; find M from density; find moles from P, V, T.

2. Graham's Law Calculations. Appears 1–2 times per NEET cycle. The formula $r_1/r_2 = \sqrt{M_2/M_1}$ is fixed — master it without inverting. Check sanity: lighter gas must be faster.

3. Molecular Speed Order and Formulas. Direct conceptual question appears almost every year: "which speed is largest?" Answer is always $v_{rms}$. Formula differences (coefficient 3 vs 8/π vs 2) are also tested.

Medium-Yield Topics (spend 30%)

4. Compressibility Factor Z Interpretation. Read Z vs P graphs. Key facts: Z = 1 ideal; Z < 1 at moderate P (attraction); Z > 1 at high P (repulsion); $H_{2}$/He always Z > 1. These graph-interpretation questions appear every 2–3 years.

5. Van der Waals Constants a and b. Know: $a$ = attraction correction, $b$ = volume correction. "High $a$ → easily liquefied." "$H_{2}$ always Z > 1 because $a$ is tiny."

6. Dalton's Law. Usually tested in the context of collecting gas over water: subtract water vapor pressure to get dry gas pressure.

Low-Yield Topics (spend 10%)

7. Critical constants ($T_c$, $P_c$, $V_c$) in terms of $a$ and $b$ — appear rarely as direct recall.
8. Boyle temperature definition — occasionally tested as a one-liner.
9. Joule-Thomson effect — conceptual definition question appears once every 3–4 years.

Exam Timing

• Ideal gas numerical: 45–60 seconds (substitute, solve, unit check)
• Graham's law numerical: 30–45 seconds (set up ratio, square root)
• Molecular speed conceptual: 15–20 seconds (direct recall)
• Z-factor graph interpretation: 30 seconds (identify the gas, read graph trend)