Covalent bonding MCQs — Chemistry (page 2)

26. How many hydrogen atoms are bonded to carbon in methane?

1. 1
2. 2
3. 3
4. 4

Answer: D) 4

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27. Which diagram would represent silicon dioxide?

1. Only silicon atoms
2. Only oxygen atoms
3. Giant network of silicon and oxygen atoms
4. Separate molecules

Answer: C) Giant network of silicon and oxygen atoms

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28. Which row contains only molecules with double bonds?

1. O₂ and CO₂
2. CH₄ and NH₃
3. H₂ and HCl
4. NH₃ and H₂O

Answer: A) O₂ and CO₂

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29. How many electrons are in the outer shell of each nitrogen atom in N₂ after bonding?

1. 2
2. 6
3. 8
4. 10

Answer: C) 8

Explanation: N≡N: each N has 5 outer electrons and shares 3 more, giving 8 — a full outer shell.

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30. Which property is shared by diamond and silicon dioxide?

1. Conduct electricity
2. Soft solids
3. High melting points
4. Contain delocalised electrons

Answer: C) High melting points

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31. Diamond is hard because

1. it contains ions
2. it has strong covalent bonds in a giant structure
3. it has weak forces between molecules
4. it contains free electrons

Answer: B) it has strong covalent bonds in a giant structure

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32. Which substance is a macromolecule?

1. Carbon dioxide
2. Ammonia
3. Diamond
4. Methane

Answer: C) Diamond

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33. Why does water have a higher boiling point than methane?

1. Stronger attractions between molecules
2. Ionic bonding
3. Metallic bonding
4. More covalent bonds

Answer: A) Stronger attractions between molecules

Explanation: Water molecules attract each other by hydrogen bonding, which is stronger than the weak forces between methane molecules.

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34. Which pair consists of giant covalent substances?

1. Diamond and silicon dioxide
2. Water and methane
3. Sodium chloride and magnesium oxide
4. Hydrogen and oxygen

Answer: A) Diamond and silicon dioxide

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35. In which molecule are all outer-shell electrons involved in bonding?

1. H₂O
2. NH₃
3. CH₄
4. HCl

Answer: C) CH₄

Explanation: In CH₄ all four outer electrons of carbon are used in C–H bonds, so there are no lone pairs. H₂O, NH₃ and HCl all keep lone pairs.

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36. Why is graphite soft?

1. Weak bonds within layers
2. Layers can slide over each other
3. It contains ions
4. It has a low density

Answer: B) Layers can slide over each other

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37. Which pair of atoms is most likely to form a covalent compound?

1. Sodium and chlorine
2. Magnesium and oxygen
3. Carbon and hydrogen
4. Potassium and bromine

Answer: C) Carbon and hydrogen

Explanation: Covalent bonds form between non-metals. Carbon and hydrogen are both non-metals; every other pair is a metal with a non-metal (ionic).

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38. Why do giant covalent structures have high melting points?

1. Strong ionic bonds
2. Strong metallic bonds
3. Strong covalent bonds throughout the structure
4. Weak intermolecular forces

Answer: C) Strong covalent bonds throughout the structure

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39. Diamond and silicon both have

1. giant covalent structures
2. ionic lattices
3. low melting points
4. mobile ions

Answer: A) giant covalent structures

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40. Which statement about ammonia is correct?

1. It is ionic.
2. It contains three covalent bonds.
3. It conducts electricity.
4. It is metallic.

Answer: B) It contains three covalent bonds.

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41. Carbon monoxide contains

1. one shared pair of electrons
2. two shared pairs of electrons
3. three shared pairs of electrons
4. no shared pairs

Answer: C) three shared pairs of electrons

Explanation: C≡O contains a triple bond — three shared pairs of electrons.

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42. How many shared electron pairs are present in ammonia (NH₃)?

1. 1
2. 2
3. 3
4. 4

Answer: C) 3

Explanation: Nitrogen forms three N–H bonds, one shared pair each, and keeps one lone pair.

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43. Graphite is used as electrodes because it

1. contains mobile electrons
2. contains ions
3. is very hard
4. is transparent

Answer: A) contains mobile electrons

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44. Which molecule contains exactly two shared electron pairs?

1. H₂
2. O₂
3. N₂
4. CH₄

Answer: B) O₂

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45. Diamond is an electrical insulator because

1. it lacks mobile charged particles
2. it has weak bonds
3. it contains molecules
4. it is soft

Answer: A) it lacks mobile charged particles

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46. Which statement about silicon dioxide is correct?

1. It has a low melting point
2. It is made of molecules
3. It has a giant covalent structure
4. It conducts electricity

Answer: C) It has a giant covalent structure

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47. How many carbon atoms is each carbon atom bonded to in diamond?

1. 2
2. 3
3. 4
4. 6

Answer: C) 4

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48. Hydrogen chloride forms a bond by

1. electron transfer
2. proton transfer
3. electron sharing
4. metallic bonding

Answer: C) electron sharing

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49. What type of forces hold simple covalent molecules together?

1. Strong ionic forces
2. Strong metallic forces
3. Weak intermolecular forces
4. Nuclear forces

Answer: C) Weak intermolecular forces

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50. Which element normally forms one covalent bond?

1. Oxygen
2. Nitrogen
3. Carbon
4. Hydrogen

Answer: D) Hydrogen

Explanation: Hydrogen has one electron and needs one more to fill its shell, so it forms exactly one bond.

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