How many NESA Chemistry questions cover Planning Investigations?

AusGrader has 12 NESA Chemistry questions on Planning Investigations, all with instant AI grading and detailed marking feedback.

NESA Chemistry Planning Investigations

1 sample question with marking guides and sample answers

Q39

2022

SCSA

16 marks

Q39

A student wanted to investigate how changing temperature would influence how rapidly oxalic acid solution would decolourise an acidified potassium permanganate solution.

The student was provided with the following chemicals and equipment:

0.1 mol L $^{-1}$ acidified potassium permanganate solution
0.1 mol L $^{-1}$ oxalic acid solution
250 mL conical flasks
Bunsen burner
tripod and gauze mat
thermometer
stop watches
5.00 mL, 10.00 mL, 20.00 mL and 25.00 mL pipettes
distilled water
25.0 mL measuring cylinders.

Q39a

2 marks

State a hypothesis for this investigation.

Answer could include:
Increasing the temperature will decrease the time taken for the acidified potassium permanganate to decolourise (change from purple to pale pink/colourless as the rate of reaction increases with increasing temperature).

Marking Criteria

Descriptor	Marks
Writes a hypothesis that gives the relationship between the independent and dependent variables.	2
Writes a hypothesis that includes the independent and dependent variables without giving their relationship.	1
None of the above	0

Q39b

2 marks

Identify the independent and dependent variables.

The independent variable is the temperature of the solution.

The dependent variable is the time taken for the potassium permanganate solution/mixture to decolourise.

Marking Criteria

Descriptor	Marks
Identifies the independent variable as temperature (of solution)	1
Identifies the dependent variable as time taken (for potassium permanganate solution/mixture) to decolourise	1

Q39c

2 marks

Identify two control variables.

Answers could include (any 2 of):

concentration of acidified potassium permanganate solution
concentration of oxalic acid solution
volume of acidified potassium permanganate solution
volume of oxalic acid solution
stopwatch/timer
person timing/observing.

Marking Criteria

Descriptor	Marks
1 mark for each correct point (any 2 of): concentration of acidified potassium permanganate solution, concentration of oxalic acid solution, volume of acidified potassium permanganate solution, volume of oxalic acid solution, stopwatch/timer, person timing/observing.	2

Q39d

6 marks

Describe a procedure for this investigation.

A possible answer:

Fixed volumes of oxalic acid and acidified potassium permanganate are used. Temperature must be varied and measured, and time must be measured from mixing. Repeated trials should be conducted.

Additionally, an appropriate method for determining the end point of the reaction (decolourisation) is used, e.g. a white paper base.

Marking Criteria

Descriptor	Marks
Recognises that fixed volumes of both oxalic acid and acidified potassium permanganate are used (1 mark for recognising fixed volume of only one)	2
Recognises that temperature must be varied and measured	1
Recognises that time must be measured from mixing	1
1 mark for each correct point (any 2 of): recognition of appropriate method for determining end point of the reaction (decolourisation) e.g. use a white paper base, recognition of the use of trials, recognition of the use of appropriate glassware, recognition that solutions are mixed in appropriate proportions e.g. 2:5 ratio of solutions	2

Q39e

4 marks

Outline the difference between systematic and random errors. Use an example of each from this investigation to support your answer.

An answer could be:

Systematic errors produce consistently high or consistently low measurements compared to the true value. Random errors produce measurements that can fluctuate around the true value.

An example of a systematic error is only heating one solution. An example of a random error is not using the same measuring equipment during the reaction.

Marking Criteria

Descriptor	Marks
Recognises that systematic errors produce consistently high or consistently low measurements compared to the true value	1
Recognises that random errors produce measurements that can be either high or low/fluctuate around the true value	1
Provides an example of a systematic error (e.g. only heating one solution, using an inappropriate proportion of reactants, errors in calibration with equipment, inappropriate rinsing of glassware)	1
Provides an example of a random error (e.g. parallax (reading of meniscus), judging the end point, use of stopwatch, reading thermometer, not using the same measuring equipment during the reaction, using measuring cylinder rather than pipette)	1

NESA Chemistry Planning Investigations

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