Topic: UNIT 5: Alkali and Alkaline Earth Metals



Topic: UNIT 5: Alkali and Alkaline Earth Metals
Q.1
For alkali metals, which one of the following trends is incorrect ?
A. Hydration energy : Li > Na > K > Rb
B. Ionisation energy : Li > Na > K > Rb
C. Density : Li < Na < K < Rb
D. Atomic size : Li < Na < K < Rb
Answer : Option C
Explaination / Solution:

Potassium is lighter than sodium (Refer table 5.3)

The correct order of density is Li < K < Na < Rb < Cs

0.54 < 0.86 < 0.97< 1.53< 1.90(in g cm–3)

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Q.2
Which of the following statements is incorrect ?
A. Li+ has minimum degree of hydration among alkali metal cations.
B. The oxidation state of K in KO2 is +1
C. Sodium is used to make Na / Pb alloy
D. MgSO4 is readily soluble in water
Answer : Option A
Explaination / Solution:

Li+ has maximum degree of hydration among alkali metal cations.

Li+ > Na+ > K+ > Rb+ > Cs+


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Q.3
Which of the following compounds will not evolve H2 gas on reaction with alkali metals ?
A. ethanoic acid
B. ethanol
C. phenol
D. none of these
Answer : Option D
Explaination / Solution:

All these compounds reacts with alkali metals to evolve hydrogen gas.

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Q.4
Which of the following has the highest tendency to give the reaction M+(g) --Aqueous ---Medium → M+(aq)
A. Na
B. Li
C. Rb
D. K
Answer : Option B
Explaination / Solution:

hydration energy of Li+ is more and hence Li+ is stabilized in aqueous medium.

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Q.5
Sodium is stored in
A. alcohol
B. water
C. kerosene
D. none of these
Answer : Option C
Explaination / Solution:
No Explaination.


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Q.6
RbO2 is
A. superoxide and paramagnetic
B. peroxide and diamagnetic
C. superoxide and diamagnetic
D. peroxide and paramagnetic
Answer : Option A
Explaination / Solution:

RbO2 is a super oxide which contains Rb+ and O2 ions. O2 contains one unpaired electron and hence it is paramagnetic.

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Q.7
Find the wrong statement
A. sodium metal is used in organic qualitative analysis
B. sodium carbonate is soluble in water and it is used in inorganic qualitative analysis
C. potassium carbonate can be prepared by solvay process
D. potassium bicarbonate is acidic salt
Answer : Option C
Explaination / Solution:

Potassium carbonate cannot be prepared by solvay process. Potassium bicarbonate is fairly soluble in water and does not precipitate out.



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Q.8
Lithium shows diagonal relationship with
A. sodium
B. magnesium
C. calcium
D. aluminium
Answer : Option B
Explaination / Solution:




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Q.9
Incase of alkali metal halides, the ionic character increases in the order
A. MF < MCl < MBr < MI
B. MI < MBr < MCl < MF
C. MI < MBr < MF < MCl
D. none of these
Answer : Option B
Explaination / Solution:

ionic character (difference in electronegativity)

MI < MBr < MCl < MF


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Q.10
In which process, fused sodium hydroxide is electrolysed for extraction of sodium ?
A. Castner's process
B. Cyanide process
C. Down process
D. All of these
Answer : Option A
Explaination / Solution:

Castner's process

NaOH ↔ Na+ + OH

Cathode : Na+ + e → Na

Anode : 2OH → H2O + 1/2O2 + 2e


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