IGCSE Chemistry: Specimen Questions with Answers 74 - 76 of 240

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Question 74

Question

MCQ▾

The number of valence electron/electrons present in alkali metals is ________.

Choices

Choice (4)

a.

4

b.

2

c.

3

d.

1

Answer

d.

Explanation

Alkali metals have only 1 valence electron.

Question 75

Write in Short

Short Answer▾

Describe a test, other than measuring pH, which can be carried out on both acid solutions to confirm the explanation given in (b) (i) for the different pH values of the two acids.

Complete the following equations for reactions of these two acids.

Explanation

Question 76

Question

MCQ▾

Carbon forms ________ bond with hydrogen.

Choices

Choice (4)

a.

Covalent

b.

Ionic

c.

All of the above

d.

None of the above

Answer

a.

Explanation

  • Carbon forms covalent bond with hydrogen. Carbon has 6 electrons. So its electronic configuration is . Thus it has electrons in its outermost shell. So carbon has valence electrons. To complete its octet carbon has to either gain electrons or lose electrons.
  • But it requires lot of energy in both the processes. So it shares its electrons. Due to presence of valence electrons carbon makes covalent bond by sharing its valence electrons with other atoms.
  • Hydrogen has 1 electron. To complete its duplet configuration it needs 1 electron. So both carbon & hydrogen share their electrons to attain their stable configurations. Thus carbon forms covalent bond with hydrogen.
  • For example in methane, each carbon atom shares its electrons with 4 hydrogen atom.
The Structure of CH4

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