Ionic Equilibrium(12th Grade > Chemistry ) Questions and answers for exam Preparation

Question 1. Review the equilibrium and choose the correct statement

H C l O_{4} + H_{2} O ⇌ H_{3} O^{+} + C l O_{4}^{-}

HClO4 is the conjugate acid of H2O
H3O+ is the conjugate base of H2O
H2O is the conjugate acid of H3O+
ClO−4 is the conjugate base of HClO4

Explanation:-

Answer: Option D. -> ClO−4 is the conjugate base of HClO4
:
D

H C l O_{4} + H_{2} O ⇌ H_{3} O^{+} + C l O_{4}^{-}

Here

H C l O_{4}

and

C l O_{4}^{-}

constitute conjugate acid and base pair.

Question 2. Electrolytes when dissolved in water dissociate into their constituent ions.
The degree of dissociation of an electrolyte increases with

Increasing concentration of the electrolyte
Decreasing concentration of the electrolyte
Decreasing temperature
Presence of a substance yielding a common ion

Explanation:-

Answer: Option B. -> Decreasing concentration of the electrolyte
:
B
The degree of dissociation is inversely proportional to the concentration of the electrolyte.

Question 3. Ammonium hydroxide is a weak base because

It has low vapour pressure
It is only slightly ionized
It is not a hydroxide of any metal
It has low density

Explanation:-

Answer: Option B. -> It is only slightly ionized
:
B
It is a weak electrolyte since slightly ionized.

Question 4. An ionizing solvent has

Low value of dielectric constant
High value of dielectric constant
A dielectric constant equal to 1
Has a high melting point

Explanation:-

Answer: Option B. -> High value of dielectric constant
:
B
Higher the dielectric constant of a solvent, more isits ionising power.

Question 5. The correct statements regarding the acids are
A)

N H_{3}

can act as both bronsted base as well as Lewis base
B) Dry hydrogen chloride is not Arrhenius acid

C) According to Davy, acid must contain oxygen as necessary element

A and B
A and C
B and C
A, B and C

Explanation:-

Answer: Option A. -> A and B
:
A
As

N H_{3}

has lone pair of electron, it can donate lone pair and can accept a proton,Arrhenius theory is limited to aqueous solutions only

Question 6. The extent of ionization increases

With the increase in concentration of solute
On addition of excess water to solution
On decreasing the temperature of solution
On stirring the solution vigorously
None of the options are correct.

Explanation:-

Answer: Option B. -> On addition of excess water to solution
:
B
withdilution of the solution.

Question 7. The dissociation constant of two acids

H A_{1}

and

H A_{2}

are

3.14 \times 10^{- 4}

and

1.96 \times 10^{- 5}

respectively. The relative strength of the acids will be approximately

1:4
4:1
1:16
16:1

Explanation:-

Answer: Option B. -> 4:1
:
B

\frac{α_{1}}{α 2} = \sqrt{\frac{K_{a 1}}{K_{a 2}}} = \sqrt{\frac{3.14 \times 10^{- 4}}{1.6 \times 10^{- 5}}}

=

4 : 1

Question 8. An electrolyte

Gives complex ions in solution
Dissolves in water to give ions
Is ionized in the solid state
Generates ions on passing electric current
None of the options are correct.

Explanation:-

Answer: Option B. -> Dissolves in water to give ions
:
B
Electrolytes are those substances which on dissolving in water give ions.

Question 9. Total number of moles for the reaction

2 H I ⇋ H_{2} + I_{2}

if

α

is degree of
dissociation is

2
1
2 - α
1 - α

Explanation:-

Answer: Option A. -> 2
:
A
Initially

2 H I ⇋ H_{2} + I_{2}

Moles of

H I = 2, H_{2} = 0, I_{2} = 0

At equilibrium,
Moles of

H I = 2 - α, H_{2} = \frac{α}{2}, I_{2} = \frac{α}{2}

Total moles =

2 - α + \frac{α}{2} + \frac{α}{2} = 2

Question 10. Which of the following is the strongest conjugate base

Cl−
CH3COO−
SO2−4
NO−2

Explanation:-

Answer: Option B. -> CH3COO−
:
B
Because it is conjugate base of weak acid.

C H_{3} C O O H ⇌ C H_{3} C O O^{-} + H^{+}