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2006 WAEC Chemistry Practical Credit will be given for strict adherence to the instructions, for observations precisely recorded and...

Chemistry
WAEC 2006

Credit will be given for strict adherence to the instructions, for observations precisely recorded and accurate inferences. All tests, observations and inferences must be clearly entered in your als book, in ink, at the time they are made.

C is a mixture of an inorganic and organic compounds. Carry out the following exercises on C: Record your.observations and identity any gases evolved. State the conclusion you draw from the result of each test.

(a) Put all of C into a beaker and add 10 cm\(^3\) of distilled water: Stir the mixture thoroughly and filter. Keep both the filtrate and residue.

(b)(i) Test the filtrate with litmus paper.

(ii) To about 2 cm\(^3\) of the filtrate, add BaCI\(_{2(aq)}\) followed by dilute HCI:

(iii) To another 2 cm\(^3\) portion of the filtrate add NaOH and heat.

(c) Transfer the residue into a boiling tube and add few drops of iodine solution

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Explanation
Test  Observation  Inference 
C + water and filter  Partially soluble in water. Colourless filtrate and white residue  C is a mixture of soluble and insoluble salt 
Filtrate + litmus paper  Turned blue litmus paper red 

Filtrate is acidic

Filtrate + BaCl\(_2\) 

ppt + dill. HCl

White precipitate 

precipitate insoluble 

CO\(_3^{2-}\), SO\(_4^{2-}\) or SO\(^{2-}_3\) present 

SO\(_4^{2-}\) present 

Filtrate + NaOH\(_{(aq)}\) + heat Gas evolved with irritating or choking or pungent smell fumed with conc. HCl or turned red litmus paper blue  Gas is NH\(_3\) from NH\(_4^+\) 
Residue + few drops of I\(_2\) solution  Blue-black or dark blue colouration  starch present 

 


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