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 Ka the acid ionization constant, then the correct relationship between α, C and Ka 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−
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,pKα=1.2,pKb =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 pKa 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.pKα of a weak acid is defined as:
a) log10 Kα
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)3 is:
a) Ksp = [Al3+] [S\(O^{2-}_4)\)
b) Ksp = [Al3+]2[S\(O^{2-}_4)\)
c) Ksp = [Al3+]3 [S\(O^{2-}_4)\)
d) Ksp = [Al3+]2[S\(O^{2-}_4)\)
ANS:
The solubility of Al2(SO4)3 =
Al2(SO4)3 ⇌ 2Al+++ + 3SO−−4
Ksp = [Al3+]2[S\(O^{2-}_4)\)
25. The unit of the ionic product of water Kw 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 ksp is:
a) 4x3
b) 108x5
c) 27x4
d) 9x
ANS:
Mg(OH)2 | ⇌ | Mg++ + 2OH− |
(X) (2X)2 |
Ksp = 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– |
\([1\times10^{-5}]\) \([2\times10^5]^2\) |
Ksp = 4 × 10−15
28. The solubility of CaF2 is 2×10−4 moles/litre. Its solubility product (Ksp) is :
a) 2.0×10−4
b) 4.0×10−3
c) 8.0×10−12
d) 3.2×10−11
ANS:
Ksp 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−] = 10−2 M
∵ 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) Ka will increase
32.Ksp 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 Ksp. ′s′is given in terms of Ksp by the relation:
ANS:
MX4 | → | M + 4X |
S 4S |
Ksp = (4s)4 s; 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. Kh (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 |