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2008 WAEC Chemistry Practical Credit will be given for strict adherence to the instructions, for observations precisely recorded, and for...

Chemistry
WAEC 2008

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

C is a mixture of two salts. Carry outline following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusion you draw from the result of each test.

(a) Put C into a beaker and add about 10 cm\(^3\) of distilled water, stir the mixture, and filter. Test the filtrate with litmus paper. Keep the residue and the filtrate.

(b)(i) To about 2 cm\(^3\) of the filtrate, add few drops of aqueous HNO\(_3\) followed by AgNO\(_{3(aq)}\) 

(ii) Add excess NH\(_3\) solution to the resulting mixture.

(c) To about half of the residue from (a) above, add about 5cm\(^3\) of dilute HNO\(_3\) in drops. Divide the resulting solution into two equal portions.

(d)(i) To the first portion add ammonia solution in drops and then in excess.

(ii) To the second portion add dilute hydrochloric acid.

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Explanation
Test Observation Inference

(a) C + water 

Mixture

filtered 

Filtrate 1 litmus 

Partly dissolves 

Colourless filtrate

white residue

No effect on litmus

C contains solution and

insoluble salts

Filtrate is neutral

(b)(i) Filtrate + dil. H\(_2\)SO\(_4\) + AgNO\(_{3(aq)}\)

(ii) Mixture in (b)(i) 

+ excess NH\(_3\) soln

No reaction

white ppt 

ppt dissolves 

Cl\(^-\) present 

 

Cl\(^-\) confirmed 

(c) Residue + dil. HNO\(_3\)  Effervescence occurs, gas turns lime water milky 

CO\(_2\)

CO\(_3^{2-}\) present 

(d)(i) First portion + dil. NH\(_3\) in drops 

then in excess 

(ii) Second portion + dil. HCl

White ppt

ppt insoluble 

White chalky ppt

Pb\(^{2+}\) may be present 

Pb\(^{2+}\) present 

Pb\(^{2+}\) confirmed 

 


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WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709