Mock Practical Test_marking Scheme

MOCK PRA CTICAL T EST

MARKING SCHEME 14th April 2009

A 1a

White precipitate is formed.

[1]

1b White ppt soluble in excess NaOH to give colourless solution.

[2]

2a White ppt. is formed. 2b White ppt is insoluble in excess aq. NH3

[1] [1]

3a

[1]

White ppt is formed.

3b No visible reaction is seen.

[1]

4

Effervescence/bubbles is seen. The gas evolved turns moist blue litmus paper red. The gas evolved is acidic gas. White ppt is formed when the gas is passed on to calcium hydroxide.

[6]

5a

White ppt. is formed.

[1]

5b White ppt. is soluble in excess NaOH to give colourless solution.

[2]

6a

[1]

White ppt is formed.

6b White ppt is insoluble in excess aq. NH3.

[1] [2]

B

R: SO42- ion

S: CO32- ion.

C

Add potassium iodide to both solution R and S. R: No visible reaction S: yellow precipitate is formed.

D

[3]

 suggest Al3+ ion is present  suggest Pb2+ ion is present

R: Al2(SO4)3 S: PbCO3

[2] Total:

- ½ m will be deducted if students write incomplete sentence. E.g. white ppt soluble in excess. ( no mention of NaOH or aq NH3)

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