NEET ChemistryUpdated 19 Oct 2026

Ionic Equilibrium: NEET PYQs and weightage

Ionic Equilibrium carries 3.4 of 100 Chemistry marks in NEET by past-paper share: 24 of the 707 tagged NEET Chemistry PYQs in the ViJEEta bank (NEET 2013–2026). It ranks 14 of 26 Chemistry chapters.

Take the 25-question Ionic Equilibrium test Formula sheet ↓All NEET Chemistry chapters

3.4/100 Weight in Chemistry

Exam importance (3/5, by past-paper share)

24 NEET PYQs

419 Practice questions

395 With measured difficulty

How the weight is computed: this chapter's tagged NEET PYQs divided by all tagged NEET Chemistry PYQs in the bank (24 of 707), times 100, with repeated questions counted once. The bank does not store the year of each NEET question, so none is printed. Computed from the bank at build time. Updated 19 Oct 2026.

Ionic Equilibrium: formula sheet for NEET

14 formulas, each with when to use it. Copy it onto one page of your notebook: that page is this chapter's handbook.

pH
$pH = - lo g [H^{+}] (1 unit of pH = 10 times change in [H^{+}])$
Use it when: you have $[H^{+}]$ and need pH, or the reverse: $[H^{+}] = 1 0^{- pH}$
Ionic product of water
$K_{w} = [H^{+}] [O H^{-}] = 1.0 \times 1 0^{- 14} (at 298 K)$
Use it when: you know one of $[H^{+}]$ or $[O H^{-}]$ and need the other
pH–pOH link
$pH + pOH = p K_{w} = 14 (at 298 K only)$
Use it when: a base problem gives $[O H^{-}]$ but asks for pH
Weak acid constant
$K_{a} = \frac{[ H ^{+} ] [ A ^{-} ]}{[ HA ]} = \frac{c α ^{2}}{1 - α}$
Use it when: a weak acid of concentration $c$ ionizes to degree $α$
Weak acid, small α
$α \approx \frac{K _{a}}{c}$
$[H^{+}] = c α \approx K_{a} c$
Use it when: $K_{a}$ is small, so $α$ is very small and $1 - α \approx 1$
Weak base constant
$K_{b} = \frac{[ B H ^{+} ] [ O H ^{-} ]}{[ B ]} = \frac{c α ^{2}}{1 - α}$
Use it when: $N H_{3}$ , an amine or any weak base ionizes in water
Weak base, small α
$α \approx \frac{K _{b}}{c}$
$[O H^{-}] = c α \approx K_{b} c$
Use it when: you need the pH of a weak base. Find pOH first, then $pH = 14 - pOH$
p-scale
$p K_{a} = - lo g K_{a}$
$p K_{b} = - lo g K_{b}$
Use it when: comparing strengths. A smaller $p K_{a}$ means a stronger acid
Conjugate pair
$K_{a} \times K_{b} = K_{w}$
$p K_{a} + p K_{b} = 14 (298 K)$
Use it when: you are given $K_{b}$ of $N H_{3}$ and asked for $K_{a}$ of $N H_{4}^{+}$ , or the reverse
Percent dissociation
$\frac{[ HA ] _{dissociated}}{[ HA ] _{initial}} \times 100 = α \times 100$
Use it when: the question asks "what % of the acid is ionized"
Common ion
$[H^{+}] = \frac{K _{a} [ HA ]}{[ A ^{-} ]}$
$[O H^{-}] = \frac{K _{b} [ B ]}{[ B H ^{+} ]}$
Use it when: the weak acid or base also has its own salt present (for example $N H_{3} + N H_{4} Cl$ ). Use the starting concentrations and neglect $x$
Very dilute strong acid
$[H^{+}] = c + x$
$where x (c + x) = K_{w}$
Use it when: the acid concentration is close to or below $1 0^{- 7} M$ , so the $H^{+}$ from water counts
Adding equilibria
$K_{net} = K_{1} \times K_{2} \times \dots$
Use it when: the target reaction is the sum of two reactions whose $K$ values you know
Polyprotic acid
$K_{a_{1}} > K_{a_{2}} > K_{a_{3}}$
Use it when: finding the pH of $H_{2} X$ or $H_{3} P O_{4}$ . Take $[H^{+}]$ from the first step only

Trap

The pH of 10⁻⁸ M HCl is not 8, because an acid can never be basic. Add water's own H⁺, which gives [H⁺] = 10⁻⁸ + x and pH ≈ 6.98.

How does NEET ask Ionic Equilibrium?

8 real previous-year questions from this chapter, as printed in the paper, each with its worked solution. Answer the first one here with no sign-in.

Q1ChemistryNEET UG PYQTheory of Acids and Bases

Try right here · No sign-in

which is the strongest acid in the following?

Answer key (C) & worked solution

Correct answer: Option C

HClO

_{4}

is the strongest acid as large number of electronegative atom attach to chlorine.

Q2ChemistryNEET UG PYQpH Calculation of Acids and Bases

The percentage of pyridine (C

_{5}

_{5}

N) that forms pyridinium ion (C

_{5}

_{5}

^{+}

H) in a 0.10 M aqueous pyridine solution (K

_{b}

for C

_{5}

_{5}

N = 1.7 × 10

^{- 9}

) is

A0.013%

B0.77%

C1.6%

D0.0060%

Answer key (A) & worked solution

Correct answer: Option A

Pyridine (C

_{5}

_{5}

N) is a weak base

K_{b} = C α^{2}

α = \frac{1.7 \times 10 ^{- 9}}{0.1}

α = 1.30 \times 1 0^{- 4}

% α = 1.30 \times 1 0^{- 4} \times 100

% α = 0.013%

Q3ChemistryNEET UG PYQSolubility and Solubility Product

MY and NY

_{3}

, two nearly insoluble salts, have the same K

_{s p}

values of 6.2 × 10−13 at room temperature. Which statement would be true in regard to MY and NY

_{3}

AThe addition of the salt of KY to solution of MY and NY

_{3}

will have no effect on their solubility

BThe molar solubility MY and NY

_{3}

in water are identical.

CThe molar solubility of MY in water is less than that of NY

_{3}

DThe salts MY and NY

_{3}

are more soluble in 0.5 M KY than in pure water.

Answer key (C) & worked solution

Correct answer: Option C

MY K

_{s p}

S_{1}^{2}

= 6.2 × 10

^{- 13}

= 62 × 10

^{- 14}

_{1}

= 7.9 × 10−7 mol/L = Solubility in pure water NY

_{3}

_{S P}

= 27

S_{2}^{4}

= 6.2 × 10

^{- 14}

_{2}

= 10-3.5 mol/L = Solubility in pure water Solubility of NY

_{3}

> solubility of MY so 3rd statements is true. Addition of KY will decrease the solubility due to common ion effect.

Q4ChemistryNEET UG PYQTheory of Acids and Bases

Amongst the given options which of the following molecules/ion acts as a Lewis acid?

_{2}

BBF

_{3}

COH–

DNH

_{3}

Answer key (B) & worked solution

Correct answer: Option B

$\left. {\begin{array}{*{20}{c}} {{H_2}O} \\ {O{H^ - }} \\ {N{H_3}} \end{array}} \right\}$ can not act as lewis acid because they does not contain vacant orbital. BF

_{3}

→ Contains vacant orbital on central atom (Boron).

Q5ChemistryNEET UG PYQTheory of Acids and Bases

Acidity of diprotic acids in aqueous solution increases in the order

_{2}

Te < H

_{2}

S < H

_{2}

_{2}

Se < H

_{2}

Te < H

_{2}

_{2}

S < H

_{2}

Se < H

_{2}

_{2}

Se < H

_{2}

S < H

_{2}

Answer key (C) & worked solution

Correct answer: Option C

In a group, the stability of hydride decreases down the group as size increases ∴ Acidity increases down the group.

Q6ChemistryNEET UG PYQSolubility and Solubility Product

The solubility of BaSO

_{4}

in water is 2.42 × 10

^{- 3}

^{- 1}

at 298 K. The value of its solubility product (K

_{s p}

) will be (Given molar mass of BaSO

_{4}

= 233 g mol

^{- 1}

)

A1.08 × 10−14 mol

^{2}

L−2

B1.08 × 10−12 mol

^{2}

L−2

C1.08 × 10−10 mol

^{2}

L−2

D1.08 × 10−8 mol

^{2}

L−2

Answer key (C) & worked solution

Correct answer: Option C

Solubility of

B a S O_{4}, s = \frac{2.42 \times 10 ^{- 3}}{233} (m o l L^{- 1})

= 1.04 \times 1 0^{- 5} (m o l L^{- 1})

B a S O_{4} (s) ⇌ B a^{2 +} (a q) + S O_{4}^{2 -} (a q)

K_{s p} = [B a^{2 +}] [S O_{4}^{2 -}] = s^{2}

= (1.04 \times 10^{- 5})^{2}

= 1.08 \times 1 0^{- 10} m o l^{2} L^{- 2}

Q7ChemistryNEET UG PYQpH Calculation of Acids and Bases

Following solutions were prepared by mixing different volumes of NaOH and HCl of different concentrations A.

60 m L \frac{M}{10} H C l + 40 m L \frac{M}{10} N a O H

55 m L \frac{M}{10} H C l + 45 m L \frac{M}{10} N a O H

75 m L \frac{M}{5} H C l + 25 m L \frac{M}{5} N a O H

100 m L \frac{M}{10} H C l + 100 m L \frac{M}{10} N a O H

pH of which one of them will be equal to 1?

Answer key (D) & worked solution

Correct answer: Option D

Meq of

H C l = 75 \times \frac{1}{5} \times 1 = 15

Meq of

N a O H = 25 \times \frac{1}{5} \times 1 = 5

Meq of HCl in resulting solution = 10 Molarity of [H

^{+}

] inresulting mixture

= \frac{10}{100} = \frac{1}{10}

p H = - lo g (H^{+}) = - lo g [\frac{1}{10}] = 1.0

Q8ChemistryNEET UG PYQSolubility and Solubility Product

The correct order of solubility of the given salts in water at 298 K is SaltK

_{sp}

298

KAgBr

5.0 \times 1 0^{- 13}

Zn (OH)_{2}

1.0 \times 1 0^{- 15}

Hg_{2} Cl_{2}

1.3 \times 1 0^{- 18}

AgBr > Zn (OH)_{2} > Hg_{2} Cl_{2}

Hg_{2} Cl_{2} > AgBr > Zn (OH)_{2}

Zn (OH)_{2} > AgBr > Hg_{2} Cl_{2}

Hg_{2} Cl_{2} > Zn (OH)_{2} > AgBr

Answer key (C) & worked solution

Correct answer: Option C

AgBr (s) ⇌ Ag^{+} (

aq.

) + Br (

aq.

)

K_{sp} = 5 \times 1 0^{- 13} = S^{2} S = 5 \times 1 0^{- 13}, S = 7.07 \times 1 0^{- 7} mol / l Zn (OH)_{2} (s) ⇌ Zn^{2 +} (aq.) + 2 OH^{-} (aq.) K_{sp} = 1 0^{- 15} = (S) (2 S)^{2} 4 S^{3} = 1 0^{- 15}, S = 0.63 \times 1 0^{- 5} = 6.3 \times 1 0^{- 6} mol / l Hg_{2} Cl_{2} (s) ⇌ Hg_{2}^{2 +} (aq.) + 2 Cl^{-} (aq.) K_{sp} = 1.3 \times 1 0^{- 18} = 4 S^{3}, S = 0.69 \times 1 0^{- 6} = 6.9 \times 1 0^{- 7} mol / l

The correct order of solubility is:

Zn (OH)_{2} > AgBr > Hg_{2} Cl_{2}

Which topics in Ionic Equilibrium carry the most questions?

The 12 busiest of 14 topics, by tagged PYQs, then practice questions. Counted from the bank. Updated 19 Oct 2026.

Topic	PYQs	Practice questions
Solubility and Solubility Product	11	98
Theory of Acids and Bases	5	47
Buffer Solutions	3	51
pH Calculation of Acids and Bases	2	61
Salt Hydrolysis	1	57
Dissociation of Weak Acids and Bases	1	26
Acid-Base Titration	1	17
pH Scale	0	26
Self-Ionization of Water	0	14
Ostwald's Dilution Law	0	10
Relationship Between Ka and Kb for a Conjugate Pair	0	5
Theory of Electrolytes	0	5

Why does Ionic Equilibrium show "–" until you answer 3 questions?

Unknown is not zero. Until you answer at least 3 graded questions in Ionic Equilibrium, ViJEEta shows – instead of a zero or a 50% default. Book exercises can raise chapter mastery up to 0.60, adaptive practice up to 0.75, and only a timed chapter test or mock can certify 0.80 and above.

How ViJEEta scores you

What happens when you test Ionic Equilibrium?

Every chapter test is 25 questions. It starts at moderate difficulty and adapts after each saved answer. If you open a solution before answering, that attempt earns no credit, so your mastery stays honest.

Start the Ionic Equilibrium test

Chapters either side of Ionic Equilibrium by weight

Aldehydes and Ketones Weight 4.0/100 p-Block Elements (Group 15 to 18) Weight 3.5/100 Some Basic Concepts of Chemistry Weight 3.4/100 Structure of an Atom Weight 3.4/100

Ionic Equilibrium: NEET PYQs and weightage

Ionic Equilibrium: formula sheet for NEET

pH

Ionic product of water

pH–pOH link

Weak acid constant

Weak acid, small α

Weak base constant

Weak base, small α

p-scale

Conjugate pair

Percent dissociation

Common ion

Very dilute strong acid

Adding equilibria

Polyprotic acid

How does NEET ask Ionic Equilibrium?

Which topics in Ionic Equilibrium carry the most questions?

Why does Ionic Equilibrium show "–" until you answer 3 questions?

What happens when you test Ionic Equilibrium?

Chapters either side of Ionic Equilibrium by weight