Ionic Equilibrium Important Questions And Answers

Ionic Equilibrium is one of the important and interesting chapters, So the practice set of Ionic Equilibrium with Important Questions And Answers helps students of class 11 and also for students studying for various competitive exams. Students are advised to practice and understand all the questions accordingly.

1. Which of the following is non-electrolyte:

a) NaCl

b) CaCl₂

c) C₁₂H₂₂O₁₁

d) CH₃COOH

ANS:

C₁₂H₂₂O₁₁ is sugar and non-electrolyte.

2. Ammonium hydroxide is a:

a) Strong electrolyte

b) Weak electrolyte

c) Both of Different conditions

d) Non-electrolyte

ANS:

It is a weak electrolyte since it is slightly ionized.

3.Electrolytes when dissolved in water dissociate into their constituent ions. The degree of dissociation of an electrolyte increases with:

a) Increasing concentration of the electrolyte

b) The decreasing concentration of the electrolyte

c) Decreasing temperature

d) Presence of a substance yielding a common ion

ANS:

Because the degree of dissociation is inversely proportional to the concentration of the electrolyte.

4. An example of a strong electrolyte is:

a) Urea

b) Ammonium hydroxide

c) Sugar

d) Sodium acetate

ANS:

CH₃COONa ⇌ CH₃COO^– + Na⁺

H₂O ⇌ H⁺ + OH^–

5. If α is the degree of ionization, C the concentration of a weak electrolyte and K_a the acid ionization constant, then the correct relationship between α, C and K_a is:

a) a= \(\sqrt{\frac{K_a}{C}}\)

b) a= \(\sqrt{\frac{C}{K}}\)

c) both

d) None of these

ANS:

According to the Ostwald’s dilution formula α²= \(\frac{K(1- α)}{C}\) But for weak electrolytes a is very small. So that (1−α) can be neglected.So that a=\(\sqrt{\frac{K_a}{C}}\).

6.The extent of ionization increases:

a) With the increase in the concentration of solute.

b) On addition of excess water to a solution.

c) Decreasing the temperature of the solution.

d) On stirring the solution vigorously.

ANS:

α ∝ dilution of solution.

7.Difference between Strong electrolytes and Weak electrolytes:

ANS:

Strong electrolytes	Weak electrolytes
Electrolytes which dissociate almost completely into constituent ions in aqueous solution	Electrolytes which dissociate to a lesser extent in aqueous solution
e.g.. all salts (except HgCl, CdBr )’ mineral acids like HCl, H₂SO4, HNO₃etc.. and bases like NaOH. KOH. etc.	All organic acids (except sulphonic acids), and bases like NH₃,NH₄OH, amines,H₃BO₃, HCN, etc.

8.Degree of Ionisation or Degree of Dissociation (α) termed as:

a) α =\(\frac{ number \,of \, molecules \,ionized \,or \,dissociated}{total \, number \,of \,molecules \,taken}\)

b) α =\(\frac{ number \,of \, atoms\,ionized \,or \,dissociated}{total \, number \,of \,molecules \,taken}\)

c) α =\(\frac{ number \,of \, molecules \,ionized \,or \,dissociated}{total \, number \,of \,atoms \,taken}\)

d) all of these

ANS:

For strong electrolytes,
α = 1
For weak electrolytes
α < 1

9. α = \(\sqrt{\frac{K}{C}}\) ⇒ α∝\({\frac{1}{\sqrt{C}}}\) is:

a) Ostwald’s Dilution Law

b) Hess’s Law

c) Gibbs energy law

d) None of these

ANS:

Here, K is dissociation constant and C is molar concentration of the solution.

10.An ionizing solvent has:

a) Low value of dielectric constant

b) High value of dielectric constant

c) A dielectric constant equal to 1

d) Has a high melting point

ANS:

higher the dielectric constant of a solvent more of its ionizing power.

11.At infinite dilution, the percentage ionisation for both strong and weak electrolytes is:

a) 1%

b) 20%

c) 50%

d) 100%

ANS:

According to Ostwald’s dilution law because the degree of ionization is directly proportional to the dilution.

12.Vant hoff factor of BaCl₂ of conc 0.01M is 1.98. Percentage dissociation of BaCl₂ on this conc.Will be.

a) 39

b) 49

c) 89

d) 49.16

ANS:

dissociation	BaCl₂	⇌	Ba²⁺ + 2Cl⁻
Initially	1		0 0
After dissociation	α – α		α 2α

Total = 1 – α + α + 2α = 1 + 2α

α = \(\frac{1.98-1}{ α}\\\) = \(\frac{0.98}{ α}\\\) = 0.49

for a mole α = 0.49 For 0.01 mole

α = \(\frac{ 0.49}{ 0.01}\\\) = 49

13. The degree of dissociation of 0.1M HCN solution is 0.01%. Its ionisation constant would be:

a) 10⁻³

b) 10⁻⁵

c) 10⁻⁷

d) 10⁻⁹

ANS:

HA ⇌ H⁺ + A⁻

\({C\alpha^2}\) = \((0.1 \times10^{-4})^2\\\)

K = \({C\alpha^2}\\\) = 10⁻⁹

14. In which of the following solutions, ions are present:

a) Sucrose in water

b) Sulphur in CS₂

c) Caesium nitrate in water

d) Ethanol in water

ANS:

It is an ionic salt.

15. Which one is the strongest electrolyte in the following:

a) NaCl

b) CH₃COOH

c) NH₄OH

d) C₆H₁₂O₆

ANS:

NaCl, being a salt, is a strong electrolyte.

16.Review the equilibrium and choose the correct statement HClO₄+ H₂O ⇄ H₃O⁺ + ClO^–₄

a) HClO₄ is the conjugate acid of H₂O

b) H₃O+ is the conjugate base of H₂O

c) H₂O is the conjugate acid of H₃O⁺

d) ClO⁻₄ is the conjugate base of HClO₄

17. A solution of FeCl₃ in water acts as acidic due to:

a) Hydrolysis of Fe³⁺

b) Acidic impurities

c) Dissociation

d) Ionisation

ANS:

FeCl₃ + 3H₂O ⇌Fe(OH)₃+ 3HCl. Strong acid and weak base.

18.For two acids A and B_,pK_α=1.2,_pK_b=2.8 respectively in value, then which is true:

a) A and B both are equally acidic

b) A is stronger than B

c) B is stronger than A

d) Neither A nor B is strong

e) None of these

ANS:

The value of _pK_a for strong acid is less.

19.Difference between lewis acid and lewis base.

ANS:

Lewis acid	Lewis base
Lewis acid is a chemical substance which can accept a pair of electrons	Lewis base is a chemical substance which can donate a pair of electrons
H⁺, K⁺, Mg²⁺, Fe³⁺, BF₃	OH-, F^–, H₂O, ROH, NH₃, H^–, CO, PR₃, C₆H₆.

20. A solution of sodium bicarbonate in water turns:

a) Phenolphthalein pink

b) Methyl orange yellow

c) Methyl orange-red

d) Blue litmus red

ANS:

NaHCO₃in water is alkaline in nature due to the hydrolysis of HCO₃^–ion. NaCO₃ ⇌ Na⁺ + HCO₃^–

21. What name is given to the reaction between hydrogen ion and hydroxyl ion:

a) Hydrogenation

b) Hydroxylation

c) Hydrolysis

d) Neutralization

ANS:

H⁺ + OH⁻⇌ H₂O, it is a neutralization reaction.

22.pK_αof a weak acid is defined as:

a) log₁₀ K_α

b) \(\frac{1}{log_{10} K_α}\)

c) log ₁₀ \(\frac{1}{K_α}\)

d) None of these

23. A salt ′X′ is dissolved in water (pH=7), the resulting solution becomes alkaline in nature. The salt is made of :

a) Strong acid and strong base

b) Strong acid and weak base

c) A weak acid and weak base

d) A weak acid and strong base

24.The expression for the solubility product of Al₂(SO4)₃is:

a) K_sp = [Al³⁺] [S\(O^{2-}_4)\)

b) K_sp = [Al³⁺]²[S\(O^{2-}_4)\)

c) K_sp = [Al³⁺]³ [S\(O^{2-}_4)\)

d) K_sp = [Al³⁺]²[S\(O^{2-}_4)\)

ANS:

The solubility of Al2(SO4)₃ =

Al₂(SO4)₃ ⇌ 2Al⁺⁺⁺ + 3SO⁻⁻₄

K_sp = [Al³⁺]²[S\(O^{2-}_4)\)

25. The unit of the ionic product of water K_w are:

a) Mol⁻¹ L⁻¹

b) Mol⁻² L⁻²

c) Mol⁻² L⁻¹

d) Mol² L⁻²

26. Let the solubility of an aqueous solution of Mg(OH)₂ be x then its k_sp is:

a) 4x³

b) 108x⁵

c) 27x⁴

d) 9x

ANS:

Mg(OH)₂	⇌	Mg⁺⁺ + 2OH⁻
		(X) (2X)²

K_sp = 4X³

27. The solubility in water of a sparingly soluble salt AB₂ is 1.0×10⁻⁵ mole l⁻¹. Its solubility product number will be:

a) 4 × 10⁻¹⁵

b) 4 × 10⁻¹⁰

c) 1 × 10⁻¹⁵

d) 1 × 10⁻¹⁰

ANS:

AB₂	⇌	A⁺ + 2B^–
		\([1\times10^{-5}]\) \([2\times10^5]^2\)

K_sp= 4 × 10⁻¹⁵

28. The solubility of CaF₂ is 2×10−4 moles/litre. Its solubility product (K_sp) is :

a) 2.0×10⁻⁴

b) 4.0×10⁻³

c) 8.0×10⁻¹²

d) 3.2×10⁻¹¹

ANS:

K_sp for CaF₂ = 4s³ =

\(4\times[2\times10^{-4}]^3\)

29.What is the pH value of \(\frac{N}{1000}\) KOH solution:

a) 10⁻¹¹

b) 3

c) 2

d) 11

ANS:

10⁻³N KOH will give [OH−] = 10⁻²M

∵ pH + pOH =14, pH = 14−2 = 12

_pOH=2

30. Which is the correct alternative for hydrolysis constant of NH₄CN:

a) \(\sqrt{\frac{K_w}{{K_a}\times{K_b}}}\\\)

b) \(\sqrt{\frac{K_w}{{K_a}\times{C}}}\\\)

c) \(\sqrt{\frac{K_w}{{K_b}\times{C}}}\\\)

d) \(\frac{K_w}{{K_a}\times{K_b}}\)

ANS:

NH₄CN is a salt of a weak acid and weak base and thus for it.

31. Which of the following will occur if a 0.1 M solution of a weak acid is diluted to 0.01M at constant temperature

a) [H+] will decrease to 0.01 M

b) pH will decrease

c) Percentage ionization will increase

d) K_a will increase

32.K_sp for sodium chloride is 36 mol²/litre2.The solubility of Sodium chloride is:

a) \(\frac{1}{36}\)

b) \(\frac{1}{6}\)

c) 6

d) 3600

ANS:

NaCl	⇌	Na⁺ + Cl^–
dissociates		S S

33. The pH of blood does not appreciably change by a small addition of an acid or a base because of blood:

a) Contains serum protein which acts as a buffer

b) Contains iron as a part of the molecule

c) Can be easily coagulated

d) It is body fluid

ANS:

the pH of blood does not change because it is a buffer solution.

34. Hydrogen ion concentration in mol/L in a solution of pH = 5.4 will be:

a) 3.98 × 10⁸

b) 3.88 × 10⁶

c) 3.68 × 10⁻⁶

d) 3.98×10⁻⁶

ANS:

pH = −log[H⁺]

5.4 = −log [H⁺]; [H⁺] =3.98 × 10⁻⁶.

35. An aqueous solution of HCl has the pH =4. Its molarity would be:

a) 4 M

b) 0.4 M

c) 0.0001 M

d) 10 M

ANS:

pH = 4 means; [H+] = 10⁻⁴ mol

36.pH + pOH equal to:

a) Zero

b) Fourteen

c) A negative number

d) Infinity

37. The molar solubility (mol L⁻¹) of a sparingly soluble salt MX₄ is ′s′. The corresponding solubility product is K_sp. ′s′is given in terms of K_sp by the relation:

ANS:

MX₄	→	M + 4X
		S 4S

K_sp = (4s)⁴s; Ksp = 256s⁵

s = \((\frac{K_{s_p}}{256})^{\frac{1}{5}}\)

38.Total number of moles for the reaction 2HI ⇄ H₂ + I₂. if α is degree of dissociation is:

a) 2

b) 2 – \(\alpha\)

c) 1

d) 1− \(\alpha\)

ANS:

2HI	⇄	H₂ + I₂
2	Initial	0 0
2 – \(\alpha\)	at equilibrium	\(\frac{\alpha}{2}\) – \(\frac{\alpha}{2}\)

2 – \(\alpha\) + \(\frac{\alpha}{2}\) + \(\frac{\alpha}{2}\)

= 2

39. K_h (hydrolysis constant) of Weak acid and weak base:

a) \(\frac{K_w}{{K_a}\times{K_b}}\)

b) \(\frac{K_w}{{K_b}}\)

c) \(\frac{K_w}{{K_a}}\)

d) \(\frac{K_b}{{K_w}}\)

40.Diffrence among Double salts Complex salts and Mixed salts:

ANS:

Double salts	Complex salts	Mixed salts
These are formed by the combination of two simple salts	These are formed by the combination of simple salts or molecular compounds.	These salts furnish more than one cation or more than one anion when dissolved in water
These exist only in solid-state,	These are stable in solid-state as well as in solutions.	Ca(OCl)Cl, NaKSO₄

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Ionic Equilibrium Important Questions And Answers