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© John Wiley & Sons Australia, Ltd 1

STUDENT:

TEACHER:

UNIT 2 — NOVEMBER EXAM

CHEMISTRY

Written test 2 Reading time: 15 minutes

Writing time: 1 hour 30 minutes

QUESTION AND ANSWER BOOK

Structure of book

Section

Number of questions

Number of questions to be answered

Number of marks

Suggested times (minutes)

A 20 20 20 20

B 10

10 64 70

Total 84 90

Instructions ● Students are permitted to bring into the test room: pens, pencils, highlighters, erasers,

sharpeners, rulers and a scientific calculator. ● Write your name in the space provided above. ● All written responses must be in English. ● Marks are awarded for correct setting out. ● Significant figures are considered as part of a correct numerical answer.

STUDYON CHEMISTRY 1 TEACHER SUPPORT KIT


Section A

Question 1 Water plays a vital role in the environment. The properties of water relate to the intramolecular and intermolecular bonding of water molecules. The unusual property of ice being less dense can be explained by:

(a) water molecules having strong covalent bonds. (b) water having a different intermolecular structure than ice. (c) there being only hydrogen bonds in water and not ice. (d) molecules being closer together in ice compared to water.

Question 2 The bonding associated with ice being less dense than water is:

(a) hydrogen bonding. (b) dipole–dipole bonding. (c) covalent bonding. (d) dispersion forces.

Question 3 Strong acids are characterised by the extent to which they ionise in water. When the strong acid HCl dissolves in excess water, the species with the lowest concentration would be:

(a) HCl (b) H2O (c) H3O+ (d) Cl–

Question 4 The pH of water samples taken from lakes near the Yallourn power station has been recorded as 4.2. The hydrogen ion concentration in the water was:

(a) 104.2 mol L–1 (b) –log 4.2 mol L–1 (c) 10–2.8 mol L–1 (d) 10–4.2 mol L–1

Question 5 Which of the following can act as a diprotic acid?

(a) NaHSO4 (b) Mg(OH)2

(c) NaH2PO4

(d) CH2Cl2



Question 6 When 20.00 mL of 0.050 mol L–1 hydrochloric acid is mixed with 30.00 mL of 0.010 mol L–1 hydrochloric acid, the molarity of the resultant mixture is:

(a) 0.026 mol L–1 (b) 0.036 mol L–1 (c) 0.043 mol L–1 (d) 0.045 mol L–1

Question 7 Which one of the following is an amphiprotic substance that is indirectly formed as a result of the combustion of fossil fuels?

(a) HNO3 (b) NaHSO4 (c) H2SO3 (d) H2SO4

Question 8 When ozone is formed in the upper atmosphere, the reaction is associated with the term:

(a) isotopes. (b) redox reaction. (c) allotropes. (d) greenhouse effect.

Question 9 Which of the following is not a redox reaction?

(a) 2Ba(s) + O2(g) → 2BaO(s) (b) Ag+(aq) + Cl–(aq) → AgCl(s) (c) Mg(s) + 2H+(aq) → Mg2+(aq) + H2(g) (d) Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)

Question 10 The oxidation number of Cl in the compound Mg(ClO)2 is:

(a) +1 (b) –1 (c) +2 (d) –2

Question 11 Consider the following equation.

4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)

How many mol of oxygen are required if you wished to produce 2.0 mol of NO?



(a) 2.0 mol (b) 2.5 mol (c) 1.6 mol (d) 5.0 mol

Question 12 Acid rain occurs partly due to the presence of sulfur dioxide in the atmosphere. The gas is formed during combustion of fossil fuels. The molecule found in living organisms that contains sulfur and contributes to acid rain is:

(a) protein. (b) carbohydrate. (c) unsaturated fats. (d) saturated fats.

Question 13 Which of the following gases does not play a direct significant role in the formation of acid rain?

(a) SO2 (b) NO2 (c) CO2

(d) CH4

Question 14 The volume of carbon dioxide produced when 10.0 mL of ethane reacts with excess oxygen according to the equation below, at constant temperature and pressure, is

2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g)

(a) 10.0 mL (b) 20.0 mL (c) 30.0 mL (d) 35.0 mL

Question 15 A major pollution issue in some cities is the formation of photochemical smog. Governments have tried to minimise this problem by:

(a) encouraging the use of CFCs in car air-conditioners. (b) insisting on the introduction of catalytic converters in car exhausts. (c) encouraging the use of LPG as an alternative fuel. (d) encouraging the use of leaded fuel.

Question 16 Which combination of chemicals would be the most practical to produce carbon dioxide in the laboratory?

(a) lithium carbonate and sodium hydroxide



(b) methane and oxygen (c) potassium carbonate and sulfuric acid (d) sodium hydroxide and hydrochloric acid

Question 17 Most governments in the world acknowledge that human activities such as agriculture have contributed to the greenhouse effect. Which of the following gases is produced as a result of agriculture and is the second most significant contributor to the greenhouse effect?

(a) CH4 (b) CO (c) O3 (d) CFCs

Question 18 The physical properties of dry ice (solid carbon dioxide) are most influenced by:

(a) dispersion forces. (b) strong intramolecular covalent bonding. (c) weak intermolecular dipole–dipole bonding. (d) significant hydrogen bonding between the CO2 molecules.

Question 19 Air consists of approximately 20% oxygen gas by volume. What mass of oxygen gas will be present in 10.0 L of air at STP?

(a) 1.43 g (b) 2.86 g (c) 7.14 g (d) 14.3 g

Question 20 Of the following, which gas is the least abundant in the atmosphere?

(a) nitrogen (b) carbon dioxide (c) oxygen (d) hydrogen

End of section A



Section B

Question 1 Large-scale municipal water-softening involves the treatment of hard water with slaked lime, calcium hydroxide, and soda ash, sodium carbonate. The water is subsequently sterilised using chlorine gas bubbled into the water.

(a) Magnesium ions react with hydroxide ions to form a precipitate. Write a chemical equation to show this reaction.

____________________________________________________________________ ____________________________________________________________________

(b) Calcium ions react with soda ash solution. Write an ionic equation to show this reaction.

____________________________________________________________________ ____________________________________________________________________

(c) The chlorine gas reacts with the water to form Cl– and HClO. Write the two half- equations for this reaction.

____________________________________________________________________ ____________________________________________________________________

(d) Write a balanced redox equation from the half-equations written in (c) above. ____________________________________________________________________ ____________________________________________________________________

(e) In the reaction given in (c) above, what is the oxidant? ____________________________________________________________________ ____________________________________________________________________

6 marks

Question 2 Normally the boiling point of a liquid matches the molar mass of the liquid molecules.

Consider the following table.

Formula of hydride in group 16 of the periodic table Boiling point (ºC) Molar mass

H2O 100 18

H2S –60 34



H2Se –40 80

H2Te –2 130

(a) Name all of the types of bonding occurring in water. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (b) H2S, H2Se and H2Te show the expected trend in boiling point and molar mass.

Explain this observation in terms of the type of bonding. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (c) Draw and label water molecules to show how bonding can explain the unexpected

boiling point of water. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (d) Solid sodium chloride dissolves readily in water.

(i) Write a chemical equation to show the reaction between sodium chloride and the solvent water.

(ii) Draw and label all bonds associated with water’s unique ability to dissolve ionic salts.

_____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________

(e) Explain why distillation is a possible desalination technique used to purify saline

solutions. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________

7 marks



Question 3 Write complete and balanced equations for the following partial equations.

(a) Mg(OH)2(aq) + H2SO4(aq) _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (b) lithium carbonate(aq) + hydrochloric acid(aq) _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (c) SO3

2–(aq) acting as a base by reacting with water _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (d) HPO4

2–(aq) acting as an amphiprotic ion by reacting with water _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (e) H2PO4

– acting as a diprotic acid by reacting with water _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________

6 marks

Question 4 The Earth’s atmosphere consists mainly of N2 and O2, as well as traces of argon, oxygen and water vapour and CO2. To determine the chemical composition of a non-polluted sample of the atmosphere, 500 L of air was collected and compressed. The total sample collected had a mass of 0.500 g. The carbon dioxide was dissolved in water and the sample was neutralised by 5.23 mL of a 0.100 mol L–1 aqueous solution of NaOH.



(a) Write a chemical equation for the reaction that occurs when CO2 reacts with excess aqueous NaOH solution to form sodium carbonate and water.

_____________________________________________________________________ _____________________________________________________________________

2 marks (b) Calculate the percentage by mass of CO2 in the atmosphere. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________

4 marks (c) Calculate the concentration, in mol L–1, of CO2 in the atmosphere. _____________________________________________________________________ _____________________________________________________________________

1 mark

Question 5 Write chemical reactions for the following situations.

(a) Ozone breaks down to form oxygen gas. _____________________________________________________________________ _____________________________________________________________________ (b) Iron(III) oxide on a rusty hammer comes in contact with an aluminium metal boat

hull. _____________________________________________________________________ _____________________________________________________________________ (c) Write the two half-reactions that occur when nitric acid formed by acid rain falls on a

galvanised iron roof. The zinc reacts with the nitric acid to form zinc nitrate and nitrogen(IV) oxide, NO2, as the major products.

_____________________________________________________________________ _____________________________________________________________________

4 marks

Question 6 Many complex chemical reactions occur in the atmosphere. The reactions associated with combustion engines make a significant contribution to atmospheric pollution.



One such reaction occurs between nitrogen and oxygen gas:

N2(g) + O2(g) → 2NO(g)

2NO(g) + O2(g) → 2NO2(g)

(a) In which of the molecules is nitrogen in the lowest oxidation state? _____________________________________________________________________ _____________________________________________________________________ (b) Which of the above molecules has undergone reduction? _____________________________________________________________________ _____________________________________________________________________ (c) The nitrogen(IV) oxide subsequently reacts with rain to form a mixture of nitric and

nitrous acids. Write a chemical equation to show this reaction. _____________________________________________________________________ _____________________________________________________________________ (d) The Acropolis in Athens is made of the rock called marble, calcium carbonate. Provide

a chemical equation to show how the nitric acid produced by acid rain can have a devastating effect on the marble.

_____________________________________________________________________ _____________________________________________________________________ (e) At 27ºC and 124.8 kPa pressure, the sample of pure atmospheric pollutant of mass

10.10 g occupies 3.15 L. Determine the molecular mass of the gas. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (f) The atmospheric pollutant mentioned in part (e) was found to contain the elements

sulfur and oxygen. Suggest an empirical formula for the gas and provide a chemical reaction to show how an oxide of sulfur reacts with rain to form an acid.

_____________________________________________________________________ _____________________________________________________________________

8 marks

Question 7 Carbon dioxide plays a vital role in the biosphere. The gas occurs in trace amounts in the atmosphere.

(a) Give two important equations that show the formation of carbon dioxide in the carbon cycle.

_____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________



(b) By means of a diagram show the preferred laboratory method of making carbon

dioxide. Label the important apparatus parts.

(c) What is the equation associated with the laboratory preparation of carbon dioxide? _____________________________________________________________________ (d) What is one important industrial use of carbon dioxide? _____________________________________________________________________ (e) What is the biochemical equation that links oxygen and carbon dioxide in the carbon

cycle? _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________

8 marks

Question 8 Consider the following atmospheric chemical equation.

2SO2(g) + O2(g) → 2SO3(g)

(a) What is the volume of sulfur trioxide, SO3, that will form at SLC when 2.50 L of sulfur dioxide reacts with an excess of oxygen gas?

_____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________



(b) If the sulfur trioxide dissolves in 25.0 mL of water, what will be the pH of this solution?

_____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ (c) Given [H+][OH–] = 10–14, what is the pH of a 0.0010 mol L–1 solution of NaOH? _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________

7 marks

Question 9 Complete the following diagram by entering the chemical formula or the name of the chemical process or reaction. Write the names or types of molecule in the solid boxes and the chemical or biochemical reactions in the dashed boxes.

7 marks

Question 10 The atmosphere consists of many gases vital to the biosphere.

(a) Which gas is the most abundant in the atmosphere? _____________________________________________________________________ (b) What is the name of the chemically unreactive gases found in the atmosphere? _____________________________________________________________________



(c) Which gas is primarily responsible for the greenhouse effect? _____________________________________________________________________ (d) Which molecule protects us from UV radiation? _____________________________________________________________________

4 marks

End of Section B