O LevelChemistryCambridgeExam Questions2. Atoms, Elements & Compounds2.5 Simple Molecules & Covalent Bonds

Simple Molecules & Covalent Bonds (Cambridge O Level Chemistry)

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2.5 Simple Molecules & Covalent Bonds

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2.5 Simple Molecules & Covalent Bonds

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11 mark

Which of the following compounds are formed by covalent bonding?

1 Potassium fluoride
2 Propane
3 Carbon dioxide
4 Lithium bromide

  • 2 and 3

  • 2 and 4

  • 1, 2 and 3

  • 1 and 4

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21 mark

Which row correctly describes a simple covalent compound?

  low melting point high boiling point
A ✓ ✓
B cross times ✓
C cross times cross times
D ✓ cross times

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    31 mark

    Which statement about bonding is not correct?

    • Covalent bonding involves non metal elements.

    • Covalent bonding involves electron sharing.

    • Covalent bonding involves electron transfer.

    • Covalent bonding does not involve metal elements.

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    41 mark

    Ammonia is a covalent compound consisting of one nitrogen atom bonded to three hydrogen atoms.

    Which statement is correct for a molecule of ammonia?

    • The number of shared pairs of electrons is five

    • The number of shared pairs of electrons is three

    • There are single covalent bonds between the hydrogen atoms.

    • Each hydrogen atom donates one pair of electrons to the central nitrogen atom.

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    51 mark

    Extended Only 

    The structure of propane is shown below
    propane

    Which correctly explains why propane can not conduct electricity?

    • There are weak intermolecular forces between molecules of propane

    • The covalent bonds in propane are strong

    • There are no free electrons able to move and carry a charge

    • Propane has a low boiling point

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    11 mark

    Atoms P and Q have electronic structures as shown in the diagram. They react together to form a covalent compound.

    q1-2-3-mcq-medium-cie-igcse-chemistry

    What is the formula of the compound?

    • P2Q3

    • P3Q

    • P3Q2

    • PQ4

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    21 mark

    The atom of element Z has 6 electrons in its outer shell. How would this element react?

    • It shares two electrons with four from another atom to form two covalent bonds

    • It shares four electrons with four from another atom to form four covalent bonds

    • It shares four electrons with two from another atom to form two covalent bonds

    • It shares two electrons with two from another atom to form two covalent bonds

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    31 mark

    CH4, H2O and HCl are covalent compounds.

    Which atoms in these compounds do not use all of their outer shell electrons in bonding?

    • C and O

    • C and H

    • Cl and O

    • Cl and C

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    41 mark

    The electronic configurations of four different atoms are shown below.

    q4-2-3-mcq-medium-cie-igcse-che

    Which atoms form covalent compounds?

    • W and X

    • W, X and Y

    • W and Z

    • X, Y and Z

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    51 mark

    Which of the following molecules contains only single covalent bonds?

    • N2

    • F2

    • O2

    • CO2

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    61 mark

    What is a covalent bond?

    • a pair of electrons shared by two non-metallic atoms

    • electrons being shared by a lattice of positively charged ions

    • elements losing electrons to achieve a noble gas structure

    • oppositely charged particles strongly attracting each other

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    71 mark

    Ethane, C2H6, and ammonia, NH3, are covalent compounds.

    The dot-and-cross diagrams of these compounds are shown.

     q9-cie-o-level-chemistry-specimen-2023-paper-1

    Which statements are correct?

    1 A molecule of ethane contains twice as many hydrogen atoms as a molecule of ammonia.
    2 An unreacted nitrogen atom has five outer electrons.
    3 In a molecule of ethane, the bond between the carbon atoms is formed by sharing two electrons, one from each carbon atom.

    • 1, 2 and 3

    • 1 and 2 only

    • 1 and 3 only

    • 2 and 3 only

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    11 mark

    Carbon dioxide is a simple molecular substance in which the molecules are formed by covalent bonding between one carbon atom and two oxygen atoms.

    Which dot and cross diagram below shows the correct outer shell arrangement of electrons in a molecule of CO2?

    q1-2-3-mcq-hard-cie-igcse-che

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      21 mark

      A student has drawn a dot and cross diagram to represent a molecule of ethene, C2H4, as shown below.

      q2-2-3-mcq-hard-cie-igcse-che

      What is wrong with the students drawing?

      • The number of electrons shared between the carbon atoms is incorrect.

      • The number of electrons shared between each carbon and hydrogen is incorrect.

      • There is nothing wrong with the drawing.

      • The total number of electrons shared is incorrect.

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      31 mark

      Dot and cross diagrams for four covalent molecules are shown below.

      Which diagram is incorrect?

      q3-2-3-mcq-hard-cie-igcse-che

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        41 mark

        Which statement about methane is correct?

        • It has a high melting point due to strong covalent bonds between atoms 

        • It has a low melting point due to weak covalent bonds between the molecules 

        • It has a low boiling point due to weak intermolecular forces between molecules 

        • It has a high boiling point because of strong intermolecular forces between molecules

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        51 mark

        A covalent molecule M contains a total of four shared electrons. 

        What is M?

        • Carbon dioxide

        • Oxygen

        • Nitrogen 

        • Methane

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