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2000 WAEC Chemistry Practical Credit will be given for strict adherence to instructions, for observations precisely recorded and for...

Chemistry
WAEC 2000

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

C is a mixture of two simple salts. Carry out the following exercises on C. Record your observations and identify any gases evolved. Sate the conclusion you draw from the result of each test.

(a) Put all of C into a beaker of boiling tube and add about 10cm\(^3\) of distilled water. Stir well and filter. Keep the residue and keep the residue and the filtrate. Test the filtrate with litmus

 

(b) Add about 1 cm\(^3\) of dilute hydrochloric acid to the residue in a test tube  and warm gently Divide the reaction mixture into two portions

(c)(i) To the first portion from (b) add saturated sodiuim trioxocarbonate (V) solution in excess

(d) To bout 2cm\(^2\) of the filtrate from (a) add a few drops of barium chloride solution followed by excess dilute hydrochloric acid 

 

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Explanation
Test Observation Inference
(a) C + water and filtered  Part or samples dissolves colourless filtrate salt. The filtrate is neutral to litmus  C is a mixture of a soluble salt 
(b) The residue + dil. HCl and warmed  Effervescence occurs, a colourles, odourless gas is given off which turns lime water milky 

The filtrate is neutral. The gas is CO\(_2\).

CO\(_3^{2-}\) present 

(i) A portion from (b) + NaOH solution dropwise and in excess  A light blue precipitate insoluble in excess of the NaOH solution 

CU\(^{2+}\) are present

(ii) The other portion of the solution from b, saturated solution or Na\(_2\)CO\(_3\) is added  Effervescence occurs, a colourless odourless gas evolved CO\(_2\). HCl are suspected
(d) To the filtrate from (a) BaCl\(_2\) and dilutes HCl were added  A white insoluble precipitate was formed 

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

SO\(_4^{2-}\) present


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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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NECO June/July 2024 - Get offline past questions & answers - Download objective & theory, all in one app 48789
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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NECO June/July 2024 - Get offline past questions & answers - Download objective & theory, all in one app 48789