The s-Block Elements Questions and Answers Part-3

1. Which of the following alkali metal form complex hydrides
a) Li
b) Na
c) K
d) Rb

Answer: a
Explanation: Li forms LiAlH4 and Na forms NaBH4 as the complex hydrides besides simple hydrides of MH type.

2. Which of the following has the highest melting point?
a) NaCl
b) NaF
c) NaBr
d) NaI

Answer: b
Explanation: NaF due to its largest lattice energy has the highest melting point

3. Which of the following has lowest melting point?
a) Li
b) Na
c) K
d) Cs

Answer: d
Explanation: Melting point of alkali metals decreases with increase in size.

4. With the increase in atomic weights melting points of the alkali metals
a) increase
b) decrease
c) remain constant
d) do not show definite trend

Answer: b
Explanation: decrease

5. Lithium shows diagonal relationship with
a) magnesium
b) beryllium
c) aluminium
d) boron

Answer: a
Explanation: Lithium shows diagonal relationship with magnesium

6. The electronic configuration of metal M is \[1s^{2},2s^{2}2p^{6},3s^{1}\]  . The formula of its oxide would be
a) MO
b) \[M_{2}O\]
c) \[M_{2}O_{3}\]
d) \[MO_{2}\]

Answer: b
Explanation: Electronic configuration indicates that the metal is univalent (alkali metal). Its oxide will be M2O.

7. Which of the following electronic configurations corresponds to an element with the lowest ionization energy ?
a) \[1s^{2} 2s^{2} 2p^{3}\]
b) \[1s^{2} 2s^{2} 2p^{5}\]
c) \[1s^{2} 2s^{2} 2p^{6}\]
d) \[1s^{2} 2s^{2} 2p^{6} 3s^{1}\]

Answer: d
Explanation: Electronic configuration of the alkali metals correspond to lowest I.E

8. Solution of sodium metal in liquid ammonia is strongly reducing due to the presence of the following in solution
a) sodium hydride
b) sodium amide
c) sodium atoms
d) solvated electrons

Answer: d
Explanation: solvated electrons

9. Lithium is strongest reducing agent among alkali metals due to which of the following factor?
a) Ionization energy
b) Electron affinity
c) Hydration energy
d) Lattice energy

Answer: c
Explanation: Li due to highest hydration energy among the alkali metals is the strongest reducing agent

10. Microcosmic salt is :
a) \[Na_{2}HPO_{4}.2H_{2}O\]
b) \[\left(NH_{4}\right)_{2}HPO_{4}.2H_{2}O\]
c) \[Na\left(NH_{4}\right)HPO_{4}.4H_{2}O\]
d) None of these

Answer: c
Explanation: \[Na\left(NH_{4}\right)HPO_{4}.4H_{2}O\]