NCERT Class XI Chemistry The s-Block Elements Solutions
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Question : 7
Total: 32
In what ways lithium shows similarities to magnesium in its chemical behaviour?
Solution:
(a) Both Li and Mg are harder and lighter than the other metals in their respective groups.
(b) Li like Mg decomposes water slowly to liberate hydrogen.
2Li +2 H 2 O H 2
Mg +2 H 2 O M g ( O H ) 2 + H 2
The hydroxides so formed are weak bases and decompose on heating.
2LiOH →L i 2 O + H 2 O M g ( O H ) 2 H 2 O
(c) Both form nitrides upon direct combination with nitrogen gas.
6Li +N 2 2 L i 3 N N 2 M g 3 N 2
(d) Both form monoxides when heated in oxygen.
4Li +O 2 2 L i 2 O O 2
The oxides do not combine with excess oxygen to give superoxides.
(e) Carbonates of Li and Mg decompose on heating.
L i 2 C O 3 L i 2 O + C O 2 M g C O 3 C O 2
(f) Both LiCl andM g C l 2
crystallise from aqueous solution as hydrates,L i C l . 2 H 2 O M g C l 2 . 6 H 2 O
(b) Li like Mg decomposes water slowly to liberate hydrogen.
2Li +
Mg +
The hydroxides so formed are weak bases and decompose on heating.
2LiOH →
(c) Both form nitrides upon direct combination with nitrogen gas.
6Li +
(d) Both form monoxides when heated in oxygen.
4Li +
The oxides do not combine with excess oxygen to give superoxides.
(e) Carbonates of Li and Mg decompose on heating.
(f) Both LiCl and
crystallise from aqueous solution as hydrates,
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