CHEMISTRY SBA1

BAC (QUALITATIVE ANALYSIS) [VERSION 1]

Link with NSS curriculum: Topic IV (Acids and Bases)

Number of period required 1 40 minutes Experimental work: 20 minutes

Prior knowledge sub-sections (a) and (d) of topic IV

Objective To test the students’ knowledge on precipitation

reactions and acid-carbonate reactions Assessment:

Mainly based on the written worksheet2

BAC (QUALITATIVE ANALYSIS) [VERSION 1]

Instructions Given: MgSO4(aq); Na2CO3(aq); Pb(NO3)2; and

HCl(aq) Perform the tests as in table below. Observations? Identification?

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BAC (QUALITATIVE ANALYSIS) [VERSION 1]

Mixing solutions

Observation

A( ) + B( )

A ( ) + C( )

A( ) + D( )

B( ) + C( )

B( ) + D( )

C( ) + D( )4

ASSESSMENT CONSIDERATIONS

Mainly based on written worksheets Any unsafe practice?

Marks to be deducted With prior notice

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MARKING CRITERIA

Mark Remarks

10 - 9 Accurate description of nearly all results.Logical deduction of the unknown.Safety procedures have been observed.

8 – 6 Accurate description of some results.Can deduce the cation / anion logically.Safety procedures have been observed.

5 – 3 Accurate description of at least one result.Can state the cation / anion.

2 – 1 Accurate description of one result ORCan state the cation / anion.

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BAC (QUALITATIVE ANALYSIS) [VERSION 1: EXEMPLAR]

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BAC (QUALITATIVE ANALYSIS) [VERSION 1: EXEMPLAR]

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In this exemplar, the student correctly identified the four substances. However, in recording his observations, he wrongly stated no observable change as no observations. Moreover, the description on his deduction is not systematic and could not convey his ideas clearly.

BAC (QUALITATIVE ANALYSIS) [VERSION 2]

Link with NSS curriculum Topic IV (Acids and Bases); Topic VII (Redox

reactions) Number of periods required

1 40 minutes The students are able to complete the

experiment and hand in the worksheet within 30 minutes.

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BAC (QUALITATIVE ANALYSIS) [VERSION 2]

1 Describe the sample.2 Estimate, using universal test paper, the pH

of an aqueous solution of the sample.

3 Report on the action of HCl on an aqueous solution of the sample.

4 Report on the action of H2SO4 on an aqueous solution of the sample.

5 Report on the action of NaOH on an aqueous solution of the sample.

6 Report on the action of aqueous NH3 on an aqueous solution of the sample.

7 Report on the action of a few drops of KMnO4 in H2SO4 on an aqueous solution of the sample.

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BAC (QUALITATIVE ANALYSIS) [VERSION 2]

Note: 2/3 of the marks are allocated to the observations. 1/3 of the marks are allocated to the interpretation of the observations and the deduction of the chemical nature of the sample.

Summarise, in the space below, your conclusions as to the chemical nature of the sample. Deduce, where possible, what ionic and / or molecular species are present in the sample.

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BAC (QUALITATIVE ANALYSIS) [VERSION 2: EXEMPLAR]

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BAC (QUALITATIVE ANALYSIS) [VERSION 2: EXEMPLAR]

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POINTS TO TAKE NOTE

Safety practice Safety goggles Safety first before assessment

Adequate number of apparatus / chemical reagents

Use reagent bottles with dropper Flame test

2 fume cupboards [F&E] Test tube vs. microscale

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