VCE CHEMISTRYUnit 2 What Makes Water Such

a Unique Chemical?

Marilyn Schell Margaret Hogan

2

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Science Press 2017First published 2017

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What Makes Water Such a Unique Chemical? iiiScience Press

Surfing VCE Chemistry Unit 2

Contents

Introduction iv

Words to Watch iv

Area of Study 1 How Do Substances Interact with Water?

Properties of Water

1 Hydrides and Their Boiling Points 2

2 Melting and Boiling Points of Group 4 16 Hydrides

3 Specific Heat Capacity of Water 5

4 Latent Heat of Water 9

5 Density of Water 10

6 Surface Tension of Water 11

7 Revision - Properties of Water 12

Water as a Solvent

8 Solubility of Molecular Substances 14

9 Solubility of Ionic Compounds 15

10 Precipitation Reactions 16

11 Water as a Solvent 18

12 Revision of Water as a Solvent 19

Acid-Base (Proton Transfer) Reactions in Water

13 Development of Ideas about Acids 21

14 The Brnsted-Lowry Theory 22

15 Acidic, Basic and Neutral Salts 24

16 Proton Donors and Acceptors 26

17 Ionic Product of Water and pH 28

18 Indicators 31

19 Calculation of pH 34

20 Acid Dissociation Constants 35

21 Strong/Weak, Concentrated/Dilute 36

22 Sulfuric Acid A Strong Acid 38

23 Reactions of Acids with Metals 40

24 Reactions of Acids with Hydroxides 41

25 Reactions of Acids with Carbonates 42

26 Acid Rain 43

27 Revision of Acid-Base Reactions in Water 46

Redox (Electron Transfer) Reactions in Water

28 Displacement of Metals 48

29 Oxidation and Reduction 50

30 Oxidant or Reductant 52

31 Types of Redox Reactions 53

32 Corrosion (A Selected Redox Issue) 56

33 Revision of Redox Reactions in Water 58

Area of Study 2 How Are Substances in Water Measured and Analysed?

Water Sample Analysis34 Distribution of Water on Earth 60

35 Sampling Protocols 62

36 Chemical Contaminants 64

37 Revision of Water Sample Analysis 66

Measurement of Solubility and Concentration38 Solubility Tables and Measurement 67

39 Temperature and Solubility 68

40 Solubility Curves 70

41 Concentration of Solutions 72

42 Other Measures of Concentration 73

43 Introduction to Analysis 75

44 Revision of Solubility and Concentration 78

Analysis for Salts in Water45 Sources of Salts in Water 80

46 Mass-Mass Stoichiometry 82

47 Gravimetric Analysis 84

48 Colorimetry and UV-Visible Spectroscopy 86

49 Atomic Absorption Spectroscopy 90

50 Revision of Analysis of Salts 93

Analysis for Organic Compounds in Water51 Sources of Organic Contaminants 95

52 Chromatography 97

53 High Performance Liquid Chromatography 98

54 Revision of Analysis for Organic Compounds 99

Analysis for Acids and Bases in Water55 Sources of Acids and Bases in Water 100

56 Volumetric Analysis 103

57 Acid-Base Titrations 105

58 Standard Solutions 107

59 Titration Equipment 108

60 Titration Procedure and Calculations 110

61 Revision of Analysis for Acids and Bases 112 in Water

62 Revision of Water A Unique Chemical 113

Topic Test 119

Answers 123

Data Sheet 153

Periodic Table 154

Index 155

What Makes Water Such a Unique Chemical?ivScience Press

Surfing VCE Chemistry Unit 2

Introduction

This book covers the Chemistry content specified in the Victorian Certificate of Education Chemistry Study Design. Sample data has been included for suggested experiments to give you practice to reinforce practical work in class.

Each book in the Surfing series contains a summary, with occasional more detailed sections, of all the mandatory parts of the syllabus, along with questions and answers.

All types of questions multiple choice, short response, structured response and free response are provided. Questions are written in exam style so that you will become familiar with the concepts of the topic and answering questions in the required way.

Answers to all questions are included.

A topic test at the end of the book contains an extensive set of summary questions. These cover every aspect of the topic, and are useful for revision and exam practice.

Words To Watch

account, account for State reasons for, report on, give an account of, narrate a series of events or transactions.

analyse Interpret data to reach conclusions.

annotate Add brief notes to a diagram or graph.

apply Put to use in a particular situation.

assess Make a judgement about the value of something.

calculate Find a numerical answer.

clarify Make clear or plain.

classify Arrange into classes, groups or categories.

comment Give a judgement based on a given statement or result of a calculation.

compare Estimate, measure or note how things are similar or different.

construct Represent or develop in graphical form.

contrast Show how things are different or opposite.

create Originate or bring into existence.

deduce Reach a conclusion from given information.

define Give the precise meaning of a word, phrase or physical quantity.

demonstrate Show by example.

derive Manipulate a mathematical relationship(s) to give a new equation or relationship.

describe Give a detailed account.

design Produce a plan, simulation or model.

determine Find the only possible answer.

discuss Talk or write about a topic, taking into account different issues or ideas.

distinguish Give differences between two or more different items.

draw Represent by means of pencil lines.

estimate Find an approximate value for an unknown quantity.

evaluate Assess the implications and limitations.

examine Inquire into.

explain Make something clear or easy to understand.

extract Choose relevant and/or appropriate details.

extrapolate Infer from what is known.

hypothesise Suggest an explanation for a group of facts or phenomena.

identify Recognise and name.

interpret Draw meaning from.

investigate Plan, inquire into and draw conclusions about.

justify Support an argument or conclusion.

label Add labels to a diagram.

list Give a sequence of names or other brief answers.

measure Find a value for a quantity.

outline Give a brief account or summary.

plan Use strategies to develop a series of steps or processes.

predict Give an expected result.

propose Put forward a plan or suggestion for consideration or action.

recall Present remembered ideas, facts or experiences.

relate Tell or report about happenings, events or circumstances.

represent Use words, images or symbols to convey meaning.

select Choose in preference to another or others.

sequence Arrange in order.

show Give the steps in a calculation or derivation.

sketch Make a quick, rough drawing of something.

solve Work out the answer to a problem.

state Give a specific name, value or other brief answer.

suggest Put forward an idea for consideration.

summarise Give a brief statement of the main points.

synthesise Combine various elements to make a whole.

How Do Substances Interact with Water?

What Makes Water Such a Unique Chemical? 1Science Press

Surfing VCE Chemistry Unit 2

VCE CHEMISTRYArea of Study 1

2

What Makes Water Such a Unique Chemical?2Science Press

Surfing VCE Chemistry Unit 2

1 Hydrides and Their Boiling Points

The element hydrogen has the smallest atoms of all elements. Hydrogen can form compounds with all other elements except group 8/18 of the periodic table. (Note that some periodic tables refer to the noble or inert gases as group 18 whereas others refer to it as group 8, and sometimes as group 0.)

A hydride is a compound formed from hydrogen and another element. Hydrides can be ionic or covalent.

Ionic hydrides consist of hydrogen combined with a metal. Examples include sodium hydride (NaH) and magnesium hydride (MgH2). Here hydrogen is the more electronegative element in each compound, so it is considered as negatively charged (H).

Covalent hydrides consist of hydrogen bonded to one or more non-metals by sharing electrons, for example, hydrogen chloride (HCl), ammonia (NH3), water (H2O), silicon tetrahydride (SiH4), phosphorus trihydride (PH3), dihydrogen sulfide (H2S). When these compounds dissolve in water they dissociate and a positively charged hydrogen ion forms (H+). This is really just a positively charged proton; it cannot exist alone, so it bonds to a water molecule, forming an hydronium ion (H3O+).

Hydrides of group 14/4

If we look at the boiling points of the hydrides of group 14/4 of the periodic table, we can see a trend.

150200

100

0

Tem

per

atur

e (

C)

Molar mass100500

SnH4

GeH4SiH4

CH4

Figure 1.1 Boiling points of the hydrides of group 14/4.

The boiling points of the group 14/4 hydrides increase as you go down the group from methane, to silicon hydride, germanium hydride and tin hydride.

Remember, melting and boiling points of covalent substances are determined by