NCEA Level Two Chemistry Revision Guide

124 Pages·10.403 MB·English

by  Kennet G. (Ed.)

NCEA LEVEL TWO
CHEMISTRY
REVISION GUIDE
2005 edition
Selected assessments with suggested answers
Really Useful Resources
REALLY USEFUL RESOURCES
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WOOLSTON
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NEW ZEALAND
ISBN (2005 edition) 1-877389-18-8
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website http://www.rur.co.nz
COPYRIGHT © 2005 Really Useful Resources Limited
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means, without the prior written permission of the copyright
owner.
The writer gratefully acknowledges NZQA and the Sixth Form External Examination for their
permission to reproduce past assessment questions.
The suggested solutions and notes are those of the author. NZQA and the Sixth Form External
Examination take no responsibility for them.
Preface
This book is intended for students preparing for NCEA Level Two Chemistry. It includes a large
number of appropriate assessments with suggested answers. There are useful hints included in
both the question and answer sections to help students achieve with excellence.
The first section of the book is a series of questions in topic order following the seven
achievement standards. The second section provides suggested answers with explanations. By
practising questions based on each achievement standard, students will become more familiar
with what is required.
Every effort has been made to make the revision guide consistent with the latest terminology and
curriculum requirements. The 2005 edition takes into account the changes that arose from the
2004 review of the achievement standards. Obviously, we have tried to eliminate mistakes, but
no doubt some remain so I apologise in advance for these. Please contact me if you dispute an
answer. Constructive feedback is always welcome.
I sincerely thank the team who helped put the book together. They include Caroline Pau,
Stephanie Woods, Anna Ferrier, Gabrielle Christenhusz, Helen Powell and Philip Arndt.
I sincerely hope that you will find this resource helpful and rewarding. I am sure that your results
will improve with its use. Good luck in Chemistry this year and in the future, and I wish you
every success in the NCEA Level 2 examination in November.
Gary Kennett
Editor
25 January 2005
CONTENTS
Carry out Qualitative Analysis (AS90305)
Guidelines p5
Perform an Acid-Base Volumetric Analysis (AS90306)
Guidelines p6
Gravimetric or Colorimetric Analysis (AS90763)
Guidelines p7
Nature of Structure and Bonding (AS90308)
Questions p8
Answers and Notes p65
Structure and Reactions of Organic Compounds (AS90309)
Questions p20
Answers and Notes p79
Principles of Chemical Reactivity (AS90310)
Questions p36
Answers and Notes p97
Oxidation-Reduction Reactions (AS90311)
Questions p51
Answers and Notes p 110
Periodic Table at end of book
Feedback and Order Forms
Copies at the back of the book.
Qualitative Analysis (AS90305) 5
QUALITATIVE ANALYSIS (AS90305)
Carry out qualitative analysis (2.1) (3 credits - INTERNAL)
You will be expected to be able to:
• carry out procedures and use knowledge of precipitation reactions to determine ions
present in solution.
Key Points:
1. A table of ions will not be provided.
2. A procedure, such as a flow chart, to assist in determining the unknown ions will be provided.
Solubility rules that are applicable will be provided.
3. Ions to be identified will be limited to: Ag+ , Al3+, Ba2+, Cu2+, Fe2+, Fe3+, Mg2", Pb2+ Na+,
NH/, Zn2t, СГ, CO2", I", NO , OH", and SO2". Na+ and NO" are identified by a
3 3 4 3
process of elimination. NH+ will be identified using its reaction with NaOH .
4
4. To gain Achievement the following will be required:
• Carry out given procedures to determine ions present in solution. Determination of the
ions must be supported by experimental observations and identification of precipitates
formed. This could include distinguishing between names pairs of anions or pairs of
cations.
5. To gain Achievement with Merit the following will be required:
• Carry out given procedures to determine ions present in solution, and justify the
identification. Determination of the ions must be supported by experimental observations
and identification of precipitates formed. Justification must include balanced equations for
the reactions where precipitates are formed.
6. To gain Achievement with Excellence the following will be required:
• Carry out given procedures, involving the formation of complex ion(s), to determine ions
present in solution, and justify the identification. Justification must include balanced
equations for the formation of complex ions. Complex ions may include FeSCN2+ and
those formed when 0H" or NH react with cations listed in 3. above, such as
(aq) 3(aq)
[Ag(NH)]+, [Al(OH)]", Pb(OH)]2", [Zn(OH)]2", [Zn(NH)]2+, and [Cu(NH)]2+.
32 4 4 4 34 34
7. The assessment task will be set by your teacher. It is not appropriate to provide sample tasks and
answers for this achievement standard.
6 Acid-Base Volumetric Analysis (AS90306)
ACID-BASE VOLUMETRIC ANALYSIS (AS90306)
Carry out an acid-base volumetric analysis (2.2) (3 credits - INTERNAL)
You will be expected to be able to:
• carry out an acid-base volumetric analysis using a given titration procedure.
Key points:
1. The titration procedure and balanced equation will be provided.
2. The standard solution to be used in the titration will be provided.
3. In solving volumetric problems, the titration data used may be that collected you, or that provided
by your teacher.
4. To gain Achievement you will be required to carry out an acid-base titration, and use titration data
to calculate the concentration of a solution.
• At least two titre values must fall within a range of 0.4 mL. The average titre value must
be within 0.8 mL of the expected outcome;
• The calculation must be carried out using an appropriate formula (not provided). Minor
errors such as numerical errors or incorrect conversion of volumes will not be penalised.
5. To gain Achievement with Merit you will be required to carry out an acid-base titration with
reasonable precision, and use titration data to correctly determine the concentration of a solution.
• At least three titre values must fall within a range of 0.4 mL. The average titre value must
be within 0.5 mL of the expected outcome;
• A titration calculation must be carried out using only concordant titre values.
6. To gain Achievement with Excellence you will be required to carry out an acid-base titration with
high precision, and use titration data from a reaction where the stoichiometry is not one-to-one, to
correctly determine the concentration of a solution.
• At least three titre values must fall within a range of 0.2 mL. The average titre value must
be within 0.2 mL of the expected outcome;
• A titration calculation where the stoichiometry is not one-to-one must be carried out
correctly using only concordant titre values. The final answer must have correct units and
an appropriate number of significant figures.
7. The assessment task will be set by your teacher. It is not appropriate to provide sample
assessment tasks and answers for this achievement standard.
Quantitative Chemical Problems (AS90763) 7
QUANTITATIVE CHEMICAL PROBLEMS (AS90763)
Solve simple quantitative chemical problems (2.3) (2 credits - INTERNAL)
You will be expected to be able to:
• Solve simple quantitative chemical problems using the relationships ancl c =
Key points:
1. To gain Achievement you will be required to solve simple quantitative problems.
• Solving simple quantitative problems may involve using the relationships n - — and
M
с = ^ to calculate one variable given the other two. Some problems may require you to
determine molar masses from given atomic masses and formulae.
2. To gain Achievement with Merit you will be required to solve quantitative problems.
• You will be required to solve problems that require an application of the relationships
n = — and c = ^. Example of suitable problems include:
- calculating % composition of a compound;
- determining empirical and molecular formulae;
- calculations involving determination of the mass of solid needed to prepare a given
volume of a standard solution;
- determining, in moles, the amount of water removed on heating a sample of a
hydrated salt to constant mass.
3. To gain Achievement with Excellence you will be required to solve complex quantitative
problems.
• Complex problems will typically involve more than two steps, and the use of
stoichiometric principles. Examples could include:
- calculating the mass of a substance produced or consumed in a reaction given the
mass of another reactant or product and the balanced equation;
- determining the number of waters of crystallisation in the formula of a hydrated salt;
- determining the concentration of a solution given titration data and the balanced
equation.
4. The assessment task will be set by your teacher. It is not appropriate to provide sample
assessment tasks and answers for this achievement standard.
8 Structure and Bonding (AS90308)
STRUCTURE AND BONDING (AS90308)
Describe the nature of structure and bonding in different substances (2.4)
(4 credits - EXTERNAL)
You will be expected to be able to:
• describe bonding in simple molecules;
• describe the nature of various types of solids.
Key points:
1. Simple molecules have no more than four electron pairs about any atom (including multiple-
bonded species). You may be required to draw Lewis structures and determine shape and
polarity.
2. Types of solids are restricted to molecular, ionic, metallic and covalent networks. The nature of
solids will be limited to the type of constituent particles (ions, atoms or molecules) and the
attractive force between them (ionic, covalent or metallic bonds, or weak intermolecular forces).
3. Properties of solids include electrical conductivity, melting point, and solubility in polar nad non-
polar solvents.
4. To gain Achievement the following will be required:
• Describe the bonding in simple molecules and the nature of solids. A description requires
you to identify, name, draw, and give characteristics, or an account of, the bonding.
5. To gain Achievement with Merit the following will be required:
• Link selected properties of simple molecules and different types of solids to their structure.
6. To gain Achievement with Excellence the following will be required:
• Discuss properties of substances in terms of structure and bonding. A discussion requires
you to show an understanding as to how or why something occurs by linking chemistry
ideas/principles. It may involve you justifying, relating, evaluating, comparing,
contrasting and/or analysing the nature or structure of bonding.
QUESTION ONE (Answerp65)
The Lewis structure for hydrogen chloride, HCl, is Ǥ- H
Draw a Lewis structure for each of the following molecules.
1. CO
2
2. PH
3
3. CHCl
2 2
4. HCO
2
5. FO
2
Strucmre and Bonding (AS90308) 9
QUESTION TWO (Answerp65)
For each of the following elements or compounds:
(a) find the total number of valence electrons in the molecule;
(b) draw a Lewis structure;
(c) give a name for the shape.
1. NH3
2. H2O
3. O
2
4. BF
3
5. F
2
6. ClO
2
7. N
2
QUESTION THREE (Answer p66)
(a) For each of the following molecules:
(i) name the shape of the molecule;
(ii) draw a diagram to clearly illustrate the named shape;
(iii) state whether the molecule is polar or non-polar.
1. HO
2
2. SO
2
3. CCl
4
4. NCl
3
(b) Explain why the molecules CCl and NCl are polar or non-polar (as described in your answer to
4 3
(a) above).
QUESTION FOUR (Answer p67)
For each of the Lewis structures below:
(a) predict the shape of the molecule (by name or 3-D diagram);
(b) state whether the molecule is polar or non-polar;
(c) explain why the molecule is either polar or non-polar.
10 Structure and Bonding (AS90308)
I
H-C-H
I
H
2.
3.
: o = c = o:
H - N -H
H
IF-S-FI
B
I
IFt
I .
H - C - Fl
IFI
QUESTION FIVE (Answer p68)
When volcanoes erupt, a number of gases may be released. These include sulfur dioxide (SO), carbon
2
dioxide (CO), hydrogen sulfide (HS) and water vapour (HO). At the surface, sulfur dioxide may also
2 2 2
oxidise to form sulfur trioxide (SO3).
Complete the table below by:
(a) (i) drawing a Lewis structure (electron dot diagram) for EACH of the formulae;
(ii) naming the shape for CO, HS, and SO
2 2 3
Formula of molecule (i) Lewis structure (ii) Name of shape
SO bent or V-shaped
2
CO
2
HS
2
H2O bent or V-shaped
SO
3