Equilibrium is one of the highest-scoring chapters in NEET Physical Chemistry, and it covers two areas students search for separately: chemical equilibrium and ionic equilibrium. This equilibrium NEET PYQ analysis brings both together, shows which question types NTA repeats, and gives you the shortcut formulas that solve most of them in under a minute.
For the full chapter-wise plan, see our complete physical chemistry guide. Equilibrium is one of its most important chapters.
Want to test yourself first? Solve the Equilibrium PYQs for free, then use this guide to fix the gaps.
Table of Contents
Why Equilibrium Carries So Many Marks
NEET usually asks two questions from Equilibrium, and sometimes three. The chapter mixes concept questions on Le Chatelier’s principle with short numericals on pH, buffers and solubility.
For the concept side of the chapter, pair this with our chemical equilibrium strategy guide. Check the NEET 2027 chapter weightage to see how it compares with other Chemistry chapters.
Equilibrium NEET PYQ Analysis: The Repeated Question Types
When you sort a decade of NEET chemistry PYQs from this chapter, the questions split into two halves.
| Question type | Half | Frequency |
|---|---|---|
| Kp–Kc relation and K manipulation | Chemical | Very frequent |
| Le Chatelier’s principle | Chemical | Very frequent |
| pH of acids, bases and salts | Ionic | Most frequent |
| Buffer solutions | Ionic | Very frequent |
| Solubility product and common ion effect | Ionic | Very frequent |
Ionic equilibrium NEET PYQs appear slightly more often than chemical equilibrium NEET PYQs, but both halves are tested every year. The thermodynamics link also matters, and our note on the thermodynamics overlap explained covers how ΔG and K connect. For a quick warm-up on each half, try these five chemical equilibrium practice questions and five ionic equilibrium practice questions.
Chemical Equilibrium: The Core Formulas
Kp = Kc (RT)^Δn, where Δn = moles of gaseous products − moles of gaseous reactants.
- If Δn = 0, Kp = Kc
- If a reaction is reversed, the new K = 1/K
- If a reaction is multiplied by n, the new K = Kⁿ
- If two reactions are added, their K values multiply
To predict the direction, compare the reaction quotient Q with K. If Q < K, the reaction moves forward. If Q > K, it moves backward. The same K logic returns in our guide to solutions and electrochemistry chapters, where it links to cell potential.
Le Chatelier’s Principle
| Change | Effect on equilibrium |
|---|---|
| Increase pressure | Shifts towards fewer gaseous moles |
| Increase temperature | Favours the endothermic direction; K of an exothermic reaction decreases |
| Add a catalyst | No shift; equilibrium is reached faster; K unchanged |
| Add inert gas at constant volume | No effect |
| Add inert gas at constant pressure | Shifts towards more gaseous moles |
Remember that only temperature changes the value of K. Many options in NEET are built to test exactly this.
Ionic Equilibrium: pH, Buffers and Solubility
pH basics
- pH = −log[H⁺], and pH + pOH = 14 at 298 K
- Kw = 1 × 10⁻¹⁴ at 298 K
- For a weak acid: [H⁺] = √(Ka · C), and the degree of dissociation α = √(Ka/C)
Buffers (Henderson equation)
pH = pKa + log([salt]/[acid])
When salt and acid concentrations are equal, pH = pKa.
Salt hydrolysis
- Salt of a strong acid and weak base: acidic
- Salt of a weak acid and strong base: basic
- Salt of a weak acid and weak base: pH = 7 + ½(pKa − pKb)
Solubility product
| Salt type | Ksp in terms of solubility s |
|---|---|
| AB (e.g. AgCl) | s² |
| AB₂ or A₂B | 4s³ |
| A₂B₃ | 108s⁵ |
A common ion lowers solubility, and precipitation occurs when the ionic product exceeds Ksp.
Worked PYQ-Pattern Questions
Q1. For N₂ + 3H₂ ⇌ 2NH₃, what is the relation between Kp and Kc?
Answer: Kp = Kc (RT)⁻². Δn = 2 − 4 = −2.
Q2. What is the pH of 10⁻³ M HCl?
Answer: 3. HCl is a strong acid, so [H⁺] = 10⁻³ M.
Q3. What is the pH of 10⁻⁸ M HCl?
Answer: Slightly less than 7 (about 6.98), not 8. At such low concentration, the H⁺ from water cannot be ignored, and an acid can never have a pH above 7.
Q4. The solubility of a salt AB₂ is s mol/L. What is its Ksp?
Answer: 4s³. Ksp = [A²⁺][B⁻]² = s × (2s)² = 4s³.
Q5. A buffer has equal concentrations of acetic acid and sodium acetate. If pKa = 4.76, what is its pH?
Answer: 4.76. When [salt] = [acid], log 1 = 0, so pH = pKa.
Common Traps in This Chapter
- Counting solid or liquid moles when finding Δn
- Thinking a catalyst changes K or shifts equilibrium
- Giving pH 8 for a very dilute strong acid
- Using s² for every salt instead of the correct Ksp expression
- Forgetting that inert gas at constant volume has no effect
Practise Every Equilibrium PYQ
This equilibrium NEET PYQ analysis gives you the formulas and patterns. Practice makes them automatic. Every previous year question from this chapter, chemical and ionic, is available chapter-wise, free:
👉 Solve all Equilibrium NEET PYQs
Solve the chemical half first, then the ionic half. Keep a list of every pH question you get wrong, because the traps repeat.
Conclusion
Equilibrium looks formula-heavy, but the same few relations answer most questions. Use this equilibrium NEET PYQ analysis to master Kp and Kc, Le Chatelier’s principle, pH, buffers and Ksp. Then practise both halves until each type feels routine.
❓ FAQ
Q: How many questions come from Equilibrium in NEET? A: Usually two questions, sometimes three, split between chemical equilibrium and ionic equilibrium.
Q: Is ionic equilibrium part of the Equilibrium chapter? A: Yes. In NCERT, the Equilibrium chapter covers both chemical equilibrium and ionic equilibrium. NEET asks questions from both parts.
Q: Does a catalyst change the equilibrium constant? A: No. A catalyst only helps the system reach equilibrium faster. Only a change in temperature changes the value of K.
Q: What is the most important topic in Equilibrium for NEET? A: pH calculations and buffers are the most tested, followed by the Kp–Kc relation, Le Chatelier’s principle and solubility product. This equilibrium NEET PYQ analysis covers each one.
Q: How do I find Ksp for AB₂? A: If the solubility is s, then [A²⁺] = s and [B⁻] = 2s, so Ksp = s × (2s)² = 4s³.
Q: Where can I practise Equilibrium NEET PYQs for free? A: You can solve every Equilibrium previous year question chapter-wise for free using the practice link in this article.