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Chemistry questions, chapter 5
Nama / NameKelas / ClassTarikh / Date

Chemical Bond

45 marks. Use Practice to check each answer as you go, or Exam to answer everything against the clock first.

Section A: objective questions

13 marks
Choose the best answer for each question.
1

Question 1

Why are noble gases unreactive and unable to form compounds?
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B
Noble gases already have a stable duplet (helium) or octet electron arrangement, so they do not need to transfer or share electrons.
For the teacher: Remembering, low difficulty, standard 5.1.1
Textbook p. 110
2

Question 2

Which half-equation shows the formation of the fluoride ion?
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A
A fluorine atom (2.7) accepts one electron to become F− (2.8).
For the teacher: Remembering, low difficulty, standard 5.2.1
Textbook p. 112
3

Question 3

Element P has proton number 12 and element Q has proton number 17. What is the formula of the compound they form?
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C
P is 2.8.2 and donates 2 electrons (P2+). Q is 2.8.7 and accepts 1 electron (Q−). Two Q ions balance one P ion, so PQ2.
For the teacher: Applying, medium difficulty, standard 5.2.1
Textbook p. 113
4

Question 4

How many pairs of electrons are shared between the atoms in a nitrogen molecule, N2?
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D
Nitrogen (2.5) needs 3 more electrons, so two atoms share 3 pairs, forming a triple bond.
For the teacher: Understanding, low difficulty, standard 5.3.1
Textbook p. 115
5

Question 5

Which molecule contains a double bond?
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B
Oxygen (2.6) shares two pairs of electrons. H2 and Cl2 have single bonds and N2 has a triple bond.
For the teacher: Remembering, low difficulty, standard 5.3.1
Textbook p. 115
6

Question 6

An atom of element Y has the electron arrangement 2.5. How many hydrogen atoms bond with one atom of Y in a covalent compound?
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C
Y has 5 valence electrons and needs 3 more for an octet, so it shares with 3 hydrogen atoms (like NH3).
For the teacher: Applying, medium difficulty, standard 5.3.1
Textbook p. 115
7

Question 7

Which compound can form hydrogen bonds between its molecules?
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A
Hydrogen bonds form when H is bonded to N, O or F. In H2O, hydrogen is bonded to oxygen. Cl, and C in CH4, do not qualify.
For the teacher: Understanding, medium difficulty, standard 5.4.1
Textbook p. 117
8

Question 8

Ethanol, C2H5OH, dissolves in water. What is the reason?
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D
The O–H group in ethanol forms hydrogen bonds with water molecules, so it dissolves.
For the teacher: Understanding, medium difficulty, standard 5.4.2
Textbook p. 119
9

Question 9

Which ion contains a dative bond?
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C
In NH4+ the nitrogen lone pair in NH3 is shared with H+, a dative bond. The other ions are simple monoatomic ions.
For the teacher: Remembering, low difficulty, standard 5.5.1
Textbook p. 120
10

Question 10

Why can a metal conduct electricity?
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B
Valence electrons are delocalised in a sea of electrons and move from the negative to the positive terminal.
For the teacher: Understanding, medium difficulty, standard 5.6.2
Textbook p. 121
11

Question 11

Table 1 shows the properties of four substances. Which substance is a giant covalent compound?
SubstanceMelting point (°C)Soluble in waterConducts electricity (solid and molten)
P801YesOnly when molten
Q−7NoNo
R1 710NoNo
S1 085NoYes
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D
R has a very high melting point, does not dissolve and does not conduct: giant covalent. P is ionic, Q is a simple molecule and S is a metal.
For the teacher: Analysing, high difficulty, standard 5.7.1
Textbook p. 128
12

Question 12

Why does sodium chloride dissolve in water?
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C
Water is a polar solvent. Its partial charges attract Na+ and Cl− and break up the lattice.
For the teacher: Understanding, medium difficulty, standard 5.7.1
Textbook p. 126
13

Question 13

A student says: "Solid sodium chloride contains ions, so it should conduct electricity." Which statement evaluates this best?
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D
Ions must be free to move to carry charge. In the solid they are fixed in the lattice; they move only when molten or dissolved.
For the teacher: Evaluating, high difficulty, standard 5.7.1
Textbook p. 125

Section B: structured questions

32 marks
Answer all questions. Write your answers in the spaces provided.
14

Question 14

Atom P has proton number 11 and atom Q has proton number 17. They react to form compound PQ.
[2 marks] (a)Write the electron arrangement of atom P and atom Q.
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[2 marks] (b)Write the half-equation for the formation of each ion.
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[1 mark] (c)State the type of bond in PQ.
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[2 marks] (d)Explain how the bond in PQ is formed.
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For the teacher: Applying, low difficulty, standard 5.2.1
Textbook p. 113
15

Question 15

Methane, CH4, is formed from carbon (proton number 6) and hydrogen (proton number 1). You are asked to draw its Lewis structure.
[1 mark] (a)State the number of valence electrons in a carbon atom and in a hydrogen atom.
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[2 marks] (b)Describe the Lewis structure you would draw.
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For the teacher: Creating, low difficulty, standard 5.3.1
Textbook p. 115
16

Question 16

Diagram 1 shows the valence electrons in a molecule of element X (X is not the actual symbol).
Two atoms of X sharing two pairs of electrons, each atom with two lone pairs
Diagram 1
[1 mark] (a)How many pairs of electrons are shared?
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[1 mark] (b)State the type of covalent bond.
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[1 mark] (c)How many valence electrons does one atom of X have?
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[2 marks] (d)X2 has a low melting point. Explain why.
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For the teacher: Analysing, medium difficulty, standard 5.3.1
Textbook p. 115
17

Question 17

Water, H2O, is a liquid at room temperature but hydrogen chloride, HCl, is a gas.
[1 mark] (a)Name the attraction force that exists between water molecules besides Van der Waals forces.
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[3 marks] (b)Explain why water is a liquid but HCl is a gas at room temperature.
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[1 mark] (c)Give one effect of hydrogen bonds in daily life.
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For the teacher: Understanding, medium difficulty, standard 5.4.2
Textbook p. 119
18

Question 18

A dative bond is formed in the ammonium ion, NH4+. [Proton number: H = 1, N = 7]
[1 mark] (a)What is a dative bond?
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[3 marks] (b)Explain the formation of the dative bond in NH4+.
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[2 marks] (c)Boron in BF3 has only six valence electrons. Can BF3 form a dative bond with NH3? Explain.
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For the teacher: Applying, high difficulty, standard 5.5.1
Textbook p. 120
19

Question 19

Table 2 shows the properties of compounds J and K.
CompoundMelting point (°C)Conducts when solidConducts when molten
J770NoYes
K80NoNo
[2 marks] (a)State the type of compound (ionic or covalent) for J and for K.
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[2 marks] (b)Explain why J conducts electricity when molten but not when solid.
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[2 marks] (c)Explain why J has a much higher melting point than K.
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For the teacher: Analysing, medium difficulty, standard 5.7.1
Textbook p. 125