O LevelChemistryCambridge (CIE)Exam Questions2. Atoms, Elements & Compounds2.5 Simple Molecules & Covalent Bonds

Simple Molecules & Covalent Bonds (Cambridge (CIE) O Level Chemistry): Exam Questions

Exam code: 5070

2 hours32 questions

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2.5 Simple Molecules & Covalent Bonds

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1
1 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

Choose your answer

2
1 mark

Which row correctly describes a simple covalent compound?

 

low melting point

high boiling point

A

✓

✓

B

×

✓

C

×

×

D

✓

×

    Choose your answer

    3
    1 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.

    Choose your answer

    4
    1 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.

    Choose your answer

    5
    1 mark

    The structure of propane is shown below

    A displayed formula. Three carbon atoms in a row joined by single lines. The left and right carbon atoms each carry three hydrogen atoms and the middle carbon carries two, all joined by single lines.

    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

    Choose your answer

    1
    1 mark

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

    Two electron shell diagrams. The first, labelled P, is a single circle carrying one electron. The second, labelled Q, has an inner circle carrying two electrons and an outer circle carrying five.

    What is the formula of the compound?

    • P2Q3

    • P3Q

    • P3Q2

    • PQ4

    Choose your answer

    2
    1 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

    Choose your answer

    3
    1 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

    Choose your answer

    4
    1 mark

    The electronic configurations of four different atoms are shown below.

    Four electron shell diagrams labelled W, X, Y and Z, with a key showing that a small circle marked e is an electron and a dashed circle is the nucleus. W has two electrons in its inner shell and one in its outer shell. X has two in the inner shell and four in the outer. Y has two in the inner shell and seven in the outer. Z has two in the inner shell and six in the outer.

    Which atoms form covalent compounds?

    • W and X

    • W, X and Y

    • W and Z

    • X, Y and Z

    Choose your answer

    5
    1 mark

    Which of the following molecules contains only single covalent bonds?

    • N2

    • F2

    • O2

    • CO2

    Choose your answer

    6
    1 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

    Choose your answer

    7
    1 mark

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

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

    Two dot-and-cross diagrams drawn without circles. The first shows two carbon atoms side by side with a pair of crosses between them, each carbon also joined to three hydrogen atoms by a pair made of one cross and one dot. The second shows a nitrogen atom joined to three hydrogen atoms, each by a pair made of one cross and one dot, with a further pair of crosses above the nitrogen.

    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

    Choose your answer

    1
    1 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?

    Four dot-and-cross diagrams labelled A to D, each showing three overlapping circles labelled O, C and O with four electrons in each overlap. In A, crosses are drawn outside both oxygen circles and two filled circles sit at the top of the carbon circle. In B, crosses are drawn outside both oxygen circles and two filled circles sit at the top of the carbon circle with two more at the bottom. In C, no electrons are drawn outside the overlaps on any circle. In D, four crosses are drawn outside each oxygen circle and none on the carbon circle.

      Choose your answer

      2
      1 mark

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

      Six circles. Two central circles labelled C overlap each other, and each also overlaps two circles labelled H. The overlap between the two carbon circles holds four electrons. Each of the four carbon to hydrogen overlaps holds two electrons. No electrons are drawn outside the overlaps.

      What is wrong with the student's 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.

      Choose your answer

      3
      1 mark

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

      Which diagram is incorrect?

      Four dot-and-cross diagrams labelled A to D. A shows two overlapping circles labelled Cl, with two crosses in the overlap, six crosses outside the right circle and none outside the left. B shows overlapping circles labelled H and Cl, with one filled circle and one cross in the overlap and six crosses outside the chlorine circle. C shows two overlapping circles labelled H, with two filled circles in the overlap and nothing outside. D shows three overlapping circles labelled O, C and O, with four electrons in each overlap and four crosses outside each oxygen circle.

        Choose your answer

        4
        1 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

        Choose your answer

        5
        1 mark

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

        What is M?

        • Carbon dioxide

        • Oxygen

        • Nitrogen 

        • Methane

        Choose your answer

        6
        1 mark

        The displayed formula of ethanoic acid is shown.

        Displayed structural formula: two carbon atoms. Left carbon has three C–H single bonds and one C–C single bond. Right carbon has one C–C single bond, one C=O double bond, and one C–O single bond to –OH.

        Which row shows the total number of shared electrons and the total number of non-bonding electrons in one molecule of ethanoic acid?

        total number of shared electrons

        total number of non-bonding electrons

        A

        14

        0

        B

        14

        8

        C

        16

        0

        D

        16

        8

          Choose your answer