Mock Practical Test_sample Answer

MOCK PRA CTICAL T EST

SAMPLE ANSWER

A 1a

Observations White precipitate is formed.

14th April 2009

Deductions Al3+, Zn2+, Pb2+ and Ca2+ may be present in R.

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

Only Al3+, Zn2+, Pb2+ may be present in R

2a

Only Al3+, Zn2+, Pb2+ may be present in R

White ppt. is formed.

2b White ppt is insoluble in excess aq. NH3

Only Al3+ or Pb2+ cations may be present in R.

3a

SO42- anion may be present in R

White ppt is formed.

3b No visible reaction is seen. 4

5a

Absence of CO32- in R because there is no effervesce observed.

Effervescence/bubbles is seen. Colourless 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.

White ppt. of Calcium Carbonate is formed. Hence, CO32- anion is present in S. Al3+, Zn2+, Pb2+ and Ca2+ may be present in S.

White ppt. is formed.

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

Only Al3+, Zn2+, Pb2+ may be present in S

6a

Only Al3+, Zn2+, Pb2+ may be present in S

White ppt is formed.

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

C

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

B) D)

Only Al3+ or Pb2+ cations may be present in S.

R: SO42- ion R: Al2(SO4)3

S: CO32- ion. S: PbCO3

Al3+ cation is present in R. Pb2+ cation is present in S.