The s-Block Elements Questions and Answers Part-2

1. The increasing order of atomic radius for the elements Na, Rb, K and Mg is
a) Na < K < Mg < Rb
b) K < Na < Mg < Rb
c) Na < Mg < K < Rb
d) Rb < K < Mg < Na

Answer: c
Explanation: Na < Mg < K < Rb

2. Smallest among these species is
a) hydrogen
b) helium
c) lithium
d) lithium ion

Answer: d
Explanation: lithium ion

3. Which of the following has largest size ?
a) Na
b) \[Na^{+}\]
c) \[Na^{-}\]
d) None of these

Answer: c
Explanation: \[Na^{-}\]

4. Which of the following alkali metal ions has the lowest mobility in aqueous solution ?
a) \[Li^{+}\]
b) \[Na^{+}\]
c) \[K^{+}\]
d) \[Cs^{+}\]

Answer: a
Explanation: Li+ is most highly hydrated [Li+ (H2O)6 ]+ . Therefore its effective size becomes greater than any other hydrated alkali metal cation and hence has the lowest mobility

5. Which of the following has the least ionization potential?
a) Li
b) He
c) N
d) Zn

Answer: a
Explanation: Li

6. In view of their low ionization energies, the alkali metals are
a) weak oxidising agents
b) strong reducing agents
c) strong oxidising agents
d) weak reducing agents

Answer: b
Explanation: Alkali metals are strong reducing agents and have less value for I.P

7. Which one of the following has highest electropositive character?
a) Cu
b) Cs
c) Ba
d) Cr

Answer: b
Explanation: Alkali metals are more electropositive and this character increases down the group

8. Which of the following has the highest conductivity ?
a) \[Li^{+}\]
b) \[Cs^{+}\]
c) \[Na^{+}\]
d) \[K^{+}\]

Answer: b
Explanation: Cs+ due to its very high ionic mobility has the highest conductivity.

9. The metal that dissolves in liquid ammonia, giving a dark blue coloured solution is
a) tin
b) lead
c) sodium
d) silver

Answer: c
Explanation: sodium

10. Highly pure dil. solution of Na in liquid ammonia
a) shows blue colour
b) exhibits electrical conductivity
c) produces sodium amides
d) produces hydrogen gas

Answer: b
Explanation: Dilute solution of Na in liquid NH3 will not produce sodium amide and hydrogen gas instantaneously. These are metastable and when catalysed give hydrogen and amide