Chem Chapter 2,3,4

First of all the check list:
AOS 1 SAC - STUDY CHECKLIST

KEY SCIENCE SKILLS

● Writing an aim and hypothesis

● Identifying independent, dependent and controlled variables

● Collection and interpretation of results and data

● Identifying errors and suggesting potential modifications

CHAPTER 2 - COVALENT BONDING

● Lewis diagrams

● Structural formulas

● Molecule shapes and how they are determined by VSEPR theory

● Linear, V-shaped/Bent, Pyramidal, Tetrahedral

● Polar and non polar molecules

● Intramolecular vs intermolecular forces and their relative strengths

● Dispersion forces, Dipole-dipole attractions, Hydrogen bonding

● Explain the properties of covalent molecules

● Melting point and boiling point

● Non-conduction of electricity

● Structure, bonding and properties of diamond and graphite and their suitability for

applications

CHAPTER 3 - REACTIONS OF METALS

● Metallic bonding model

● Explain the properties of metals

● Hard

● Melting and boiling points

● Conduction of electricity and heat

● Malleable and ductile

● Lustrous

● Reactions of metals with acids, water and oxygen

● Circular vs Linear economy

● Metal recycling

CHAPTER 4 - REACTIONS OF IONIC COMPOUNDS

● Ionic bonding model

● Explain the properties of ionic compounds

● Hard and brittle

● Melting point

● Electrical conductivity - differences between solid and molten/aqueous states

● Writing and naming ionic formulas - including polyatomic ions and transition metals

● Using solubility table to predict whether a precipitate will form

● Writing balanced full and ionic equations for precipitation reactions (including states)




These are answers to chapter 2 questions:
SECTION A: Multiple-choice questions (1 mark each)

Question 1

Answer: C

Explanation:

Ammonia has the strongest intermolecular force as it is able to form hydrogen bonds with

adjacent molecules.

Question 2

Answer: B

Explanation:

Ammonia is pyramidal as the nitrogen bonds to three hydrogens with one lone pair of electrons.

Question 3

Answer: D

Explanation:

Propene would have the highest boiling point as it is the longest molecule.

Question 4

Answer: B

Explanation:

Oxygen has two pairs of non-bonding electrons or oxygen molecules have four pairs of non-

bonding electrons

Question 5

Answer: D

Explanation:

Hydrogen bonds occur when hydrogen is bonded to fluorine, nitrogen or oxygen

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Question 6

Answer: B

Explanation:

The strongest intermolecular force in hydrogen sulfide is dipole-dipole attraction as there is a

difference in electronegativity of hydrogen and sulfur, but not to the same degree as fluorine,

nitrogen or oxygen.

Question 7

Answer: B

Explanation:

Ethane is non-polar therefore the only force holding together adjacent molecules is dispersion

forces.

Question 8

Answer: D

Explanation:

Fluoromethane is the only non-symmetrical tetrahedral molecule in the list, methane and

tetrachloromethane are symmetrical and ammonia is pyramidal.

Question 9

Answer: C

Explanation:

Diamond conducts heat as the atoms are able to vibrate and pass energy to adjacent atoms, but

there are no free moving charged particles to conduct electricity.

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Question 10

Answer: B

Explanation:

Graphite is a covalent layer lattice.

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SECTION B: Short-answer questions

Question 1

Molecule Lewis diagram Structural formula Shape Polarity

Water (H2O) V-shaped or

bent Polar

Ethane (C2H6) Linear Non-polar

Nitrogen (N2) Linear Non-polar

Carbon dioxide

(CO2)

Linear Non-polar

Ammonia (NH3) Pyramidal Polar

Question 2

a.

Diamond Graphite

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b.

i. Diamond forms covalent bonds with four adjacent carbon atoms*, whereas

graphite forms bonds with three adjacent carbon atoms, leaving one electron free

to conduct a charge*.

ii. Diamond and graphite both have strong bonds to adjacent carbon atoms*, these

allow the vibration of the heat energy to be conducted through the material*.

iii. Diamond forms covalent bonds with four adjacent carbon atoms giving it strong

bonds in all directions so cannot be scratched*, whereas graphite forms bonds with

three adjacent carbon atoms forming a layer, these layers can be easily scratched*.

2 + 2 + 2 = 6 marks

Total 10 marks

Question 3

a. Covalent substances do not have free moving electrons in their structure*, therefore they

cannot conduct electricity*.

2 marks

b. Hexane is a longer molecule (6 carbons) than butane (4 carbons)*, therefore there are more

dispersion forces holding them together, so it has a higher boiling point*.

2 marks

c. Ethanol has an oxygen bonded to a hydrogen therefore is able to form hydrogen bonds

between adjacent molecules*, whereas ethane is symmetrical so only has dispersion forces

holding together adjacent molecules*.

2 marks

d. Water has an oxygen bonded to a hydrogen therefore is able to form hydrogen bonds between

adjacent molecules*, whereas carbon dioxide is symmetrical so only has dispersion forces

holding together adjacent molecules*.

2 marks

e. Graphite has layers of strong covalent carbon bonds* that require a large amount of energy to

break*.

Now chapter 3:
SECTION A: Multiple-choice questions (1 mark each)

Question 1

Answer: C

Explanation:

All metals conduct electricity and heat, and are ductile, however not all metals have a high

melting point.

Question 2

Answer: D

Explanation:

The metallic bonding model has positive cations surrounded by a sea of delocalised electrons.

Question 3

Answer: C

Explanation:

The metallic bonding model can explain why metals are malleable and ductile (there is space in

the sea of electrons for cations to move) and why metals are good conductors of heat (particles

are able to vibrate and transfer energy), but cannot explain why they exist in solid and liquid state

at room temperature or why some are magnetic.

Question 4

Answer: D

Explanation:

A highly reactive metal produces hydrogen and metal hydroxide (a base) when placed in water.

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Question 5

Answer: D

Explanation:

The reactivity of metals decreases from left to right and increases from top to bottom.

Question 6

Answer: B

Explanation:

Metals are malleable as cations are able to be moved inside the metallic lattice.

Question 7

Answer: B

Explanation:

A reactive metal produces hydrogen and a salt when placed in water.

Question 8

Answer: B

Explanation:

The most reactive metal in the list is sodium (group 1) and the least reactive is silver.

Question 9

Answer: D

Explanation:

A metal ore is a naturally occurring mineral that a metal can be extracted from profitably.

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Question 10

Answer: A

Explanation:

The balanced equation for the step in the Bayer process is

Al2O3 + 2NaOH  2NaAlO2 + H2O

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SECTION B: Short-answer questions

Question 1

a.

i. Iron can be mined from iron ore and made into steel or steel can be recycled from sources

that are no longer required*.

ii. Steel can be used to create new products*.

iii. Manufacturing of steel products should be as close to the point of sale as possible or

distributed using low emission transport options*.

iv. Steel items should be reused or repaired rather than just replaced*.

v. Steel can be easily sorted from other waste by the use of magnets*.

vi. Steel can be melted and remade into new products.

1 + 1 + 1 + 1 + 1 + 1 = 6 marks

b. Any two of:

 Reduces the waste and landfill

 Reduces the impact of mining

 Requires less energy than extracting from ore

 Reduces the impact of transportation of iron ore and products

2 marks

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Question 2

a. The independent variable is the metal.

1 mark

b. The dependent variable is the results of the test (water, acid and oxygen).

1 mark

c. Metal B was not tested in acid as it reacted vigorously with water.

1 mark

d. The order of reactivity is B – A – C – E – D.

1 mark

e. Any suitable method that identifies the following:

 A suitable experiment

 An explanation of the process

 An explanation of the theory behind the experiment

 An explanation of how the metals will be put in order

A possible answer could be “Another experiment that could order the reactivity of the metals

would be to place the metals that did not react vigorously with water in solutions of the other

metals*. Reactive metals will be displaced by less reactive metals in the solution*. The most

reactive metal will be displaced by all other metals*, the least reactive will not be displaced*.

4 marks

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Question 3

a.

3 marks

b.

i. Cations are able to be moved in the sea of electrons as the electrons are constantly moving

(delocalized) so the bonds are constantly forming and breaking so force and heat can

change the shape of metals or draw them into wires.

2 marks

ii. Free moving electrons are able to move and transfer energy through the metal.

2 marks

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iii. The electrons in the sea of delocalized electrons reflect photons off the smooth surface of

the metals.

2 marks

iv. Strong electrostatic forces of attraction exist between the positive cations and the negative

sea of electrons.

This interaction is responsible for the high electrical conductivity and malleability observed in metallic substances.

Now chapter 4:
SECTION A: Multiple-choice questions (1 mark each)

Question 1

Answer: B

Explanation:

NH3, CO2 and NO2 are covalent substances, whereas Ag2SO4, NH4NO3, and CuO are all ionic

substances.

Question 2

Answer: C

Explanation:

The ionic lattice contains metal cations and non-metal anions in a 3D lattice.

Question 3

Answer: D

Explanation:

Ionic compounds have high melting points and conduct electricity in the molten and aqueous

states, but they are brittle not malleable.

Question 4

Answer: C

Explanation:

Ammonium, nitrate and potassium salts are always soluble, silver chloride is insoluble.

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Question 5

Answer: A

Explanation:

Potassium and nitrate salts are always soluble, lead iodide is the precipitate.

Question 6

Answer: C

Explanation:

The solution with the largest number of ions, K2SO4 has three ions, NH4Cl has two ions, Na3PO4

has four ions, Ba(NO3)2 has three ions, therefor Na3PO4 has the highest conductivity.

Question 7

Answer: A

Explanation:

Potassium and sulfate both remain dissolved in the solution and therefore are the spectator ions.

Question 8

Answer: C

Explanation:

Ionic compounds are held together by the electrostatic force of attraction between positive metal

cations and negative non-metal anions.

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Question 9

Answer: D

Explanation:

In chemistry, hardness relates to the ability of a material to be scratched. Ionic compounds are

hard because the surface of the crystal lattice is not easily scratched.

Question 10

Answer: B

Explanation:

Aluminium ions have a charge of 3+ and carbonate ions have a charge of 2-, therefore we need

two aluminium ions for every three carbonate ions (Al2(CO3)3).

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SECTION B: Short-answer questions

Question 1

a.

i.

ii. The advantages of this model include; it shows how the anions and cations are formed by

the transfer of electrons* and it shows the ratio of metal ions to non-metal ions that are

required*.

iii. Disadvantages of this model include; it does not show the arrangement of the ions in the

lattice* and it does not show the relative size of the ions

1 + 2 + 2 = 5 marks

b.

i.

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ii. The advantages of this model include any two of; It shows the arrangement of the atoms in

a single layer, it is easier to draw than the 3D model, it shows the correct ratio of cations to

anions.

iii. Disadvantages of this model include any two of; It only shows a single layer of the lattice,

it does not show how the layers are arranged, it only shows one possible arrangement of the

lattice.

1 + 2 + 2 = 5 marks

c.

i.

ii. The advantages of this model include any two of; It shows the 3D arrangement of the ions

around each other, it shows the correct ratio of cations to anions.

iii. Disadvantages of this model include any two of; it is difficult to draw, it is not drawn to

scale, it does not show how ions are formed.

1 + 2 + 2 = 5 marks

Total 15 marks

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Question 2

Marking scheme for question 2, 1 mark balanced full equation, 1 mark balanced ionic equation, 1

mark for correct states in both equations.

a. Full Equation: CH3COOAg (aq) + NaCl (aq)  CH3COONa (aq) + AgCl (s)

Ionic equation: Ag+

(aq) + Cl-

(aq)  AgCl (s)

3 marks

b. Full Equation: 3K2CO3 (aq) + 2Al(NO3)3 (aq)  6KNO3 (aq) + Al2(CO3)3 (s)

Ionic equation: 2Al3+ (aq) + 3CO3

2-

(aq)_  Al2(CO3)3 (s)

3 marks

c. Full Equation: 2(NH4)3PO4 (aq) + 3CuSO4 (aq)  3(NH4)2SO4(aq) + Cu3(PO4) 2 (s)

Ionic equation:2 PO4

3-

(aq) + 3Cu

2+(aq)  Cu3(PO4) 2 (s)

3 marks

Total 9 marks

Question 3

a. Ionic compounds have strong electrostatic forces of attraction between cations and anions,

however if the lattice becomes misaligned* the like charges repel, and the substance breaks

easily*.

2 marks

b. In the molten state there are ions that are free to move around and conduct a charge*, whereas

in the solid state they are held in fixed positions*.

2 marks

c. The positive hydrogen and negative oxygen dipoles in water are able disrupt the ionic

lattice*, this allows some ionic substances to dissociate and dissolve in water*.