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The s-Block Elements

Multiple Choice Questions

171.

Which of the following compounds has the lowest melting point?

CaBr₂
CaI₂
CaF₂
CaF₂

496 Views

172.

Which one of the following is present as an active ingredient in bleaching powder for bleaching action?

Ca(OCl)₂
CaO₂Cl
CaCl₂
CaCl₂

503 Views

173.

On heating which of the following releases CO₂ most easily?

K₂CO₃
Na₂CO₃
MgCO₃
MgCO₃

1639 Views

174.

What is the value of electron gain enthalpy of Na⁺ if IE₁ of Na = 5.1 eV?

-5.1 eV
-10.2 eV
+2.55 eV
+2.55 eV

594 Views

175.

Match (I) with list (II) for the compositions of substances and select the correct answer using the code given below the lists.

	List I (substance)		List II Composition
A.	Plaster of Paris	1.	CaSO₄.2H₂O
B.	Epsomite	2.	CaSO₄. ½ H₂O
C.	Kieserite	3.	MgSO₄. 7H₂O
D.	Gypsum	4. 5.	MgSO₄.H₂O CaSO₄

A

B

C

D

3

4

1

2
A

B

C

D

2

3

4

1
A

B

C

D

1

2

3

5
A

B

C

D

1

2

3

5

437 Views

176.
Property of the alkaline earth metals that increases with their atomic number

the solubility of their hydroxides in water

the solubility of their sulphates in water

ionisation energy

ionisation energy

the solubility of their hydroxides in water

Electronegativity, as well as ionisation energy both, usually decrease on moving downward a group with an increase in atomic number. The hydroxides and sulphates of alkaline earth metals are ionic solids and the solubility of ionic solids is governed by two factors viz, lattice energy and hydration energy. For solubility hydration, energy > lattice energy.
Hydration energy varies inversely with size, ie, decreases with increase in size. However, lattice energy in case of sulphates, remains almost same with an increase in the atomic number of alkaline earth metals, due to the large size of sulphates ion. Hence, hydration energy only governs the solubility of alkaline earth metal sulphates decrease as the hydration energy decreases on moving downward the II A group.

On the other hand, in the case of hydroxides, the lattice energies are different because of medium size of hydroxide ions and decreases on moving from Be to Ba. This tends to increase the solubility and to overcome the counter-effect produced by the decrease in hydration energy. Hence, the solubility of alkaline earth metal hydroxides increases with increase in the atomic number of alkaline earth metals.

553 Views

177.

Which of the following alkaline earth metal sulphates has hydration enthalpy higher than the lattice enthalpy?

CaSO₄
BeSO₄
BaSO₄
BaSO₄

410 Views

178.

In the case of alkali metals, the covalent character decreases in the order

MCl> MI>MBr>MF
MF> MCl> MBr>MI
MF > MCl> MI>MBr
MF > MCl> MI>MBr

481 Views

179.

The alkali metals form salt-like hydrides by the direct synthesis at elevated temperature. The thermal stability of these hydrieds decreases in which of the following orders?