The s-Block Elements

Question 225
CBSEENCH11008466

Which of the following oxides is most acidic in nature?

  • MgO

  • BeO

  • CaO

  • BaO

Solution

B.

BeO

In metals moving down the group metallic character increases, so basic nature increases hence most acidic will be BeO.

Question 226
CBSEENCH11008471

Among CaH2, BeH2, BaH2, the order of ionic character is

  • BeH2< CaH2<BaH2

  • CaH2<BeH2<BaH2

  • BaH2<BeH2<CaH2

  • BeH2 < BaH2 < CaH2

Solution

A.

BeH2< CaH2<BaH2

Smaller the size cation, more will be its polarising power. Hence, BeH2 will be least ionic.

Or

On moving down the group metallic character of metals increases so ionic character of metal hydride increases.

Question 227
CBSEENCH11008482

Which of the following is the correct order of stability for the given superoxides?

  • KO2 < RbO2 < CsO2

  • CsO2 < RbO2<KO2

  • RbO2

  • KO2 < CsO2 <RbO2

Solution

A.

KO2 < RbO2 < CsO2

With a progressive increase in the size of alkali metal ions, the stability of superoxides increases because the size of superoxide ion is large and large cation can be stabilised more by large anion. 

Therefore, the order of stability is

KO2 <RbO2 < CsO2

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