C HEMISTRY SBA 1

BAC (Q UALITATIVE ANALYSIS ) [V ERSION 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 worksheet 2

BAC (Q UALITATIVE ANALYSIS ) [V ERSION 1] Instructions Given: MgSO 4 (aq); Na 2 CO 3 (aq); Pb(NO 3 ) 2 ; and HCl(aq) Perform the tests as in table below. Observations? Identification? 3

BAC (Q UALITATIVE ANALYSIS ) [V ERSION 1] Mixing solutions Observation A( ) + B( ) A ( ) + C( ) A( ) + D( ) B( ) + C( ) B( ) + D( ) C( ) + D( ) 4

A SSESSMENT CONSIDERATIONS Mainly based on written worksheets Any unsafe practice? Marks to be deducted With prior notice 5

M ARKING CRITERIA MarkRemarks Accurate description of nearly all results. Logical deduction of the unknown. Safety procedures have been observed. 8 – 6Accurate description of some results. Can deduce the cation / anion logically. Safety procedures have been observed. 5 – 3Accurate description of at least one result. Can state the cation / anion. 2 – 1Accurate description of one result OR Can state the cation / anion. 6

BAC (Q UALITATIVE ANALYSIS ) [V ERSION 1: EXEMPLAR] 7

8 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 (Q UALITATIVE ANALYSIS ) [V ERSION 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. 9

BAC (Q UALITATIVE ANALYSIS ) [V ERSION 2] 1Describe the sample. 2Estimate, using universal test paper, the pH of an aqueous solution of the sample. 3Report on the action of HCl on an aqueous solution of the sample. 4Report on the action of H 2 SO 4 on an aqueous solution of the sample. 5Report on the action of NaOH on an aqueous solution of the sample. 6Report on the action of aqueous NH 3 on an aqueous solution of the sample. 7Report on the action of a few drops of KMnO 4 in H 2 SO 4 on an aqueous solution of the sample. 10

BAC (Q UALITATIVE ANALYSIS ) [V ERSION 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. 11

BAC (Q UALITATIVE ANALYSIS ) [V ERSION 2: EXEMPLAR] 12

BAC (Q UALITATIVE ANALYSIS ) [V ERSION 2: EXEMPLAR] 13

P OINTS 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 14