N
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR TEACHER USE
NZQA
Approved
Internal Assessment Resource
Chemistry Level 2
This resource supports assessment against:
Achievement Standard 91162 version 2
Carry out procedures to identify ions present in solution
Resource title: Which Ion?
3 credits
This resource:

Clarifies the requirements of the standard

Supports good assessment practice

Should be subjected to the school’s usual assessment quality assurance
process

Should be modified to make the context relevant to students in their school
environment and ensure that submitted evidence is authentic
Date version published by
Ministry of Education
February 2015 Version 2
Quality assurance status
These materials have been quality assured by NZQA.
To support internal assessment from 2015
NZQA Approved number: A-A-02-2015-91162-02-5418
Authenticity of evidence
Teachers must manage authenticity for any assessment from
a public source, because students may have access to the
assessment schedule or student exemplar material.
Using this assessment resource without modification may
mean that students’ work is not authentic. The teacher may
need to change figures, measurements or data sources or set
a different context or topic to be investigated or a different text
to read or perform.
This resource is copyright © Crown 2015
Page 1 of 9
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR TEACHER USE
Internal Assessment Resource
Achievement Standard Chemistry 91162: Carry out procedures
to identify ions present in solution
Resource reference: Chemistry 2.2A v2
Resource title: Which Ion?
Credits: 3
Teacher guidelines
The following guidelines are supplied to enable teachers to carry out valid and
consistent assessment using this internal assessment resource.
Teachers need to be very familiar with the outcome being assessed by Achievement
Standard Chemistry 91162. The achievement criteria and the explanatory notes
contain information, definitions, and requirements that are crucial when interpreting
the standard and assessing students against it.
Context/setting
This activity requires students to use given qualitative procedures to identify ions
present in a number of solutions.
Conditions
This assessment activity is designed to take place over 1–2 periods of in-class time.
Adjust these conditions to suit your students and context.
Resource requirements

red litmus paper

1 mol L-1 HCl (aq)

0.1 mol L-1 AgNO3 (aq)

0.1 mol L-1 BaCl2 (aq)

1 mol L-1 NH3 (aq)

1 mol L-1 NaOH (aq)

0.1 mol L-1 KSCN (aq)

1 mol L-1 H2SO4 (aq)

Unknown solutions:
o
A: NaCl
o
B: Na2SO4
o
C: Na2CO3
o
D: Cu(NO3)2
This resource is copyright © Crown 2015
Page 2 of 9
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR TEACHER USE

o
E: Ba(NO3)2
o
F: Pb(NO3)2
o
G: Mg(NO3)2
safety goggles, test tubes, test tube racks, test tube brushes, droppers.
Additional information
You should not use the activity exactly as it is (same ions in same order) since it is
available to all students and the assessment schedule includes examples of
appropriate responses. For example, you could substitute the ions given in this
activity with other appropriate ions (see EN 5).
The teacher could substitute the flow chart given in the student resources for an
alternative flow chart/procedure that would enable students to identify the ions in
solutions.
You should carry out tests prior to the assessment to ensure that students will be
able to identify the ions with the solutions provided.
This resource is copyright © Crown 2015
Page 3 of 9
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR STUDENT USE
Internal Assessment Resource
Achievement Standard Chemistry 91162: Carry out procedures
to identify ions present in solution
Resource reference: Chemistry 2.2A v2
Resource title: Which Ion?
Credits: 3
Achievement
Carry out procedures to
identify ions present in
solution.
Achievement with Merit
Carry out procedures to
justify the identification of
ions present in solution.
Achievement with
Excellence
Carry out procedures to
comprehensively justify the
identification of ions present
in solution.
Student instructions
Introduction
This assessment activity requires you to use given qualitative procedures to identify
ions present in a number of solutions. You will then write a report to support the
identification of the ions in the solutions.
You will be assessed on how well you carry out these given procedures to identify
the ions in the solutions.
Your teacher will guide you about how much time you will have for this activity.
This is an individual activity.
Task: Identifying Ions in Solutions
Use the aqueous solutions and the procedures in the flow charts provided in Student
Resources A and B to identify the anions present in unknown solutions A – C and the
cations present in unknown solutions D – G.
Complete all the necessary procedures for solutions A – G, identify as many ions as
possible and write equations to support your identification.
Method

Carry out procedures to identify the ion in each unknown solution using the
aqueous solutions and the flow charts provided in Student Resources A and B.

Record the steps you used to identify the ions and any observations you made
during the procedures. Use this primary data to identify the ions in the solutions.

For each ion identified:
–
name the ion present in the solution
–
describe the steps you used to identify the ion
–
describe the observations you made during each step of the procedure
This resource is copyright © Crown 2015
Page 4 of 9
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR STUDENT USE
–
identify by name or formula all precipitates formed
–
write balanced equations for all the reactions where precipitates are formed
–
–
write balanced equations for all the reactions where complex ions are formed
link your observations to any equations you write for the formation of
precipitates and/or complex ions.
This resource is copyright © Crown 2015
Page 5 of 9
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR STUDENT USE
Student Resource A:
Testing for anions flow charts: Cl-, CO32-, I-, NO3-, OH-, SO42no bubbles: OH-
Add red litmus
litmus turns blue
add dilute HCl
solution
bubbles: CO32-
litmus stays red
new sample
add AgNO3
solution
yellow
precipitate
precipitate
remains: I-
add dilute NH3
solution
white precipitate
precipitate
dissolves: Cl-
no precipitate
new sample
add BaCl2
solution
no precipitate:
NO3precipitate:
SO42-
This resource is copyright © Crown 2015
Page 6 of 9
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR STUDENT USE
Student Resource B:
Testing for cations flow chart: Ag+, Al3+, Ba2+, Cu2+, Fe2+, Fe3+, Mg2+, Pb2+, Na+, Zn2+
no precipitate:
Na+
green
precipitate: Fe2+
orange
precipitate
Add 2 drops
NaOH
new sample
add 2 drops
KSCN solution
dark red
solution: Fe3+
blue precipitate;
deep blue
solution in
excess: Cu2+
blue precipitate
brown
precipitate
new sample
add 2 drops,
then excess
NH3 solution
brown
precipitate;
dissolves in
excess: Ag+
white precipitate
add excess
NaOH solution
precipitate
dissolves
new sample
add 2 drops,
then excess,
NH3 solution
new sample
add dilute
H2SO4 solution
precipitate
remains
colourless
solution: Mg2+
white precipitate:
Ba2+
white precipitate
which dissolves
in excess: Zn2+
white
precipitate: Pb2+
white precipitate
which remains
in excess
This resource is copyright © Crown 2015
new sample
add dilute
H2SO4 solution
Page 7 of 9
colourless
solution: Al3+
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR TEACHER USE
Assessment schedule: Chemistry 91162 Which Ion?
Evidence/Judgements for Achievement
The student identifies the majority of ions (4),
including the majority of ions which form
precipitates (3/6), correctly.
The student supports their identification of 4 ions
with experimental observations.
For each of the 4 ions, the student identifies by
name or formula all precipitates formed and
supports their responses with the evidence
required.
For example:
Solution F is Pb2+
When 2 drops of NaOH are added a white
precipitate forms. The precipitate is lead hydroxide
/ Pb(OH)2(s)
When excess NaOH is added the precipitate
dissolves.
When 2 drops of NH3 are added to a new sample
a white precipitate forms. The precipitate is lead
hydroxide / Pb(OH)2(s).
When excess aqueous NH3 is added the
precipitate remains.
When H2SO4 is added to a new sample a white
precipitate forms. The precipitate is lead sulphate /
PbSO4(s).
Evidence/Judgements for Achievement with
Merit
Evidence/Judgements for Achievement with
Excellence
The student identifies the majority of ions (4),
including the majority of ions which form
precipitates (3/6), correctly.
The student supports their identification of 4 ions
with experimental observations.
For each of the 4 ions, the student identifies by
name or formula all precipitates formed, justifies
their identification of the ions, writes balanced
equations for all of the reactions where
precipitates are formed, and links all precipitation
equations to the observations made during the
procedure.
The student supports their responses with the
evidence required.
The student identifies the majority of ions (6),
including the majority of ions which form
precipitates (3/6) and the majority of ions that form
complex ions (2/3), correctly.
The student supports their identification of 6 ions
with experimental observations.
For each of the 6 ions, the student identifies by
name or formula all precipitates formed,
comprehensively justifies their identification of the
ions, writes balanced equations for all of the
reactions where precipitates and complex ions are
formed, and links all precipitation and complex ion
equations to the observations made during the
procedure.
For example:
The student supports their responses with the
evidence required.
Solution F is Pb2+
When 2 drops of NaOH are added a white
precipitate forms. The precipitate is lead hydroxide
/ Pb(OH)2(s):
Pb2+(aq)
+ 2 OH (aq)  Pb(OH)2(s).

When excess NaOH is added the precipitate
dissolves.
When 2 drops of NH3 are added to a new sample
a white precipitate forms. The precipitate is lead
hydroxide / Pb(OH)2(s):
For example:
Solution F is Pb2+
When 2 drops of NaOH are added a white
precipitate forms. The precipitate is lead hydroxide
/ Pb(OH)2(s):
Pb2+(aq) + 2 OH(aq)  Pb(OH)2(s)
When excess NaOH is added the precipitate
dissolves:
Pb2+(aq) + 2 OH(aq)  Pb(OH)2(s)
When excess aqueous NH3 is added the
This resource is copyright © Crown 2015
Pb(OH)2(s) + 2 OH(aq)  [Pb(OH)4]2(aq)
or
Page 8 of 9
Internal assessment resource Chemistry 2.2A v2 for Achievement Standard 91162
PAGE FOR TEACHER USE
precipitate remains.
When H2SO4 is added to a new sample a white
precipitate forms. The precipitate is lead sulphate /
PbSO4(s):
Pb2+(aq) + SO42(aq)  PbSO4(s).
Pb2+(aq) + 4 OH(aq)  [Pb(OH)4]2(aq)
When 2 drops of NH3 are added to a new sample
a white precipitate forms. The precipitate is lead
hydroxide / Pb(OH)2(s):
Pb2+(aq) + 2 OH(aq)  Pb(OH)2(s)
When excess aqueous NH3 is added the
precipitate remains.
When H2SO4 is added to a new sample a white
precipitate forms. The precipitate is lead sulphate /
PbSO4(s):
Pb2+(aq) + SO42(aq)  PbSO4(s)
Final grades will be decided using professional judgement based on a holistic examination of the evidence provided against the criteria in the
Achievement Standard.
This resource is copyright © Crown 2015
Page 9 of 9