S Block Elements(12th Grade > Chemistry ) Questions and answers for exam Preparation

12th Grade > Chemistry

S BLOCK ELEMENTS MCQs

Total Questions : 30 | Page 2 of 3 pages

Question 11. In the purification of NaCl, an impure solution is saturated with HCl gas. The principle involved is:

Common ion effect and low solubility of MgCl2 and CaCl2 when compared to NaCl
Common ion effect and high solubility of MgCl2 and CaCl2 when compared to NaCl
KSP of NaCl is greater than that of MgCl2
KSP of NaCl is greter than that of CaCl2 but less than that of MgCl2

Discuss Question

Answer: Option B. -> Common ion effect and high solubility of MgCl2 and CaCl2 when compared to NaCl
:
B
As

C l^{-}

concentration increases precipitation takes place.

Question 12. The ionic radii of alkali metal ions in water (hydrated radii) are in the order

Li+>Na+>K+>Rb+
Li+(aq.)>Na+(aq.)>K+(aq.)>Rb+(aq.)>Cs+(aq.)
Li+K+>Rb+>Cs+
Li+(aq.)>Na+(aq.)

Discuss Question

Answer: Option B. -> Li+(aq.)>Na+(aq.)>K+(aq.)>Rb+(aq.)>Cs+(aq.)
:
B
If we just look at only the ionic radii - then clearly

L i^{+}

should be the smallest and common sense might compel us to think that the small ion should exhibit the best conductivity. However, among alkali metal cations -

L i^{+}

has the highest charge density and is thus hydrated to the largest extent. Thus

L i^{+}

has the highest hydrated ion radius and least conductivity in water.

Question 13. Which of the following statements are correct
I. Both

L i C l

and

M g C l_{2}

are soluble in ethanol
II. Both

L i C l

and

M g C l_{2}

are deliquescent
III.

L i C l

and

M g C l_{2}

form hydrates like

L i C l .8 H_{2} O

and

M g C l_{2} .2 H_{2} O

IV.

N a H C O_{3}

used as fire extinguisher

I, II, III correct
I, II, IV correct
Only III correct
All are correct

Discuss Question

Answer: Option B. -> I, II, IV correct
:
B
Options I, II and IV are all very accurate. These are all characteristics of the corresponding compounds. As for option III - the compounds

L i C l

and

M g C l_{2}

both form hydrates. Only -

L i C l

forms

L i C l .2 H_{2} O

whereas

M g C l_{2}

forms

M g C l_{2} .8 H_{2} O

Question 14.

Li2O2 Na2O2 K2O2
Li2O Na2O2 KO2
LiO2 Na2O KO2
Li2O Na2O K2O

Discuss Question

Answer: Option B. -> Li2O Na2O2 KO2
:
B
Li forms monoxide, Na forms peroxide, K forms super oxide on burning with oxygen

Question 15. The correct statements among the following are:
I. Due to greater polarizing power of

L i^{+}

L i_{2} C O_{3}

is most stable
II.

L i H C O_{3}

does not exist as solid
III.

N a N O_{3}

on strong heating gives

N a N O_{2}

whereas

L i N O_{3}

will give

L i_{2} O

IV. Sodium & Potassium ions are involved in the transport of sugars and amino acids into the cells
V.

L i F

is less soluble due to smaller hydration energy of

L i^{+}

ion

I, II & V
III, IV & V
II, III & IV
I, III & V

Discuss Question

Answer: Option C. -> II, III & IV
:
C

L i_{2} C O_{3}

is unstable and

L i^{+}

has high hydration energy.

Question 16. Cs⁺ ions impart violet colour to Bunsen flame. This is due to the fact that the emitted radiations are of

High energy
Lower frequencies
Longer wavelength
Zero wave number

Discuss Question

Answer: Option A. -> High energy
:
A
Violet belongs to the high-energy (low wavelength) section in the visible part of the Electromagnetic spectrum.

Question 17. Solution of sodium metal in liquid ammonia is strongly reducing due to the presence of the following in solution

Sodium hydride
Sodium amide
Sodium atoms
Solvated electrons

Discuss Question

Answer: Option D. -> Solvated electrons
:
D
The (strongly) reducing nature is due to solvated or ammoniated electrons.

Question 18. Assertion (A): Sodium metal is stored in kerosene
Reason (R): The density of sodium is less than water

A and R are true & R is the correct explanation of A
A and R are true but the R is not the correct explanation of A
A is true, R is false
A is false, R is true

Discuss Question

Answer: Option B. -> A and R are true but the R is not the correct explanation of A
:
B
Sodium is stored under kerosene because it does not react with kerosene. On the other hand, Sodium violently reacts with water.
Taken one by one - both the assertion and reason are true but the reason does not explainthe assertion.

Question 19. Which of the following compounds is consumed during the preparation of