The s-Block Elements Questions and Answers Part-10

1. The most electronegative alkaline earth metal is
a) Be
b) Mg
c) Ca
d) Ba

Answer: a
Explanation: The most electronegative alkaline earth metal is Be

2. Which of the following metals has the highest melting point ?
a) Be
b) Mg
c) Ca
d) Ba

Answer: a
Explanation: Being small and hard, Be atoms pack closely in the lattice and hence Be has the highest

3. Which of the following has exceptionally high melting point
a) MgO
b) NaOH
c) NaCl
d) KCl

Answer: a
Explanation: Higher the charge on the ions, greater is the lattice energy and hence higher the of the ionic solid

4. The compounds of alkaline earth metals have the following magnetic nature
a) diamagnetic
b) paramagnetic
c) ferromagnetic
d) antiferromagnetic

Answer: a
Explanation: M2+ ions are present in alkaline earth metal compounds thus leaving all paired electrons in (n-1) s2p6 configuration and are diamagnetic.

5. Among the alkaline earth metals, the element forming predominantly covalent compound is
a) Ba
b) Sr
c) Ca
d) Be

Answer: d
Explanation: Be

6. As the nuclear charge increases from neon to calcium, the orbital energies
a) increase
b) increase very rapidly
c) increase very slowly
d) decreases

Answer: d
Explanation: After neon (At No-18), the next electron enters into 4s orbital which has lower energy than 3d orbitals

7. The following compounds have been arranged in order of their increasing thermal stabilities. Identify the correct order
a) I < II < III < IV
b) IV < II < III < I
c) IV < II < I < III
d) II < IV < III < I

Answer: b
Explanation: IV < II < III < I

8. One which is not dissolved by dilute hydrochloric acid is
a) ZnS
b) MnS
c) \[BaCO_{3}\]
d) \[BaSO_{4}\]

Answer: d
Explanation: \[BaSO_{4}\]

9. The hydroxide which is best soluble in water is
a) \[Ba\left(OH\right)_{2}\]
b) \[Mg\left(OH\right)_{2}\]
c) \[Sr\left(OH\right)_{2}\]
d) \[Ca\left(OH\right)_{2}\]

Answer: a
Explanation: \[Ba\left(OH\right)_{2}\]

10. The order solubility in water of alkaline earth metal sulphates down the group is Be > Mg > Ca > Sr > Ba. This is due to increases in
a) ionization energy
b) melting point
c) coordination number
d) All of these

Answer: c
Explanation: In crystalline sulphates, the co-ordination number of the ions increases from Be to Ba and so also the lattice energy hence solubility in H2O decreases