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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