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2012 WAEC Chemistry Practical Credit will be given for strict adherence to the instructions, for observations precisely recorded, and for accurate...

Chemistry
WAEC 2012

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 entered in your answer book, in ink, at the time they are made. 

C and D are two aqueous solutions. Carry out the following exercises on C and D. Record your observations and identify any gas(es) evolved. State the conclusion you draw from the result of each test.

(a)(i) To about 2 cm\(^3\) portion of C, add NaOH\(_{(aq)}\) In drops until in excess. Warm the mixture

(ii) To another 2 cm\(^3\) portion of C, add HCl\(_{(aq)}\) followed by BaCl\(_{2(aq)}\)

 

(b)(i) (ii) To another 2 cm\(^3\)  portion of D, add add NH\(_{3(aq)}\) drops and then in excess.

 (ii) To about 2 cm\(^3\) portion of D, add AgNO\(_{3(aq)}\)  followed by HNO\(_{3(aq)}\) 

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Explanation
TEST OBSERVATION INFERENCE

(a)(i) C + NaOH\(_{(aq)}\) + warm 

 

 

 

(ii) C + HCl\(_{(aq)}\) + BaCl\(_{2(aq)}\)

 

(b)(i) D + NH\(_{3(aq)}\)

 

(ii) D + AgNO\(_{3(aq)}\) + HNO\(^{3(aq)}\)

No visible reaction/no pot 

A colourless gas with pungent/choking/irritating smell evolved.

Gas turned damp red litmus blue/formed white fumes with conc HCl vapour 

 

No visible reaction while ppt formed 

Reddish - brown/brown ppt

ppt insoluble 

 

White ppt

ppt insoluble

Gas is NH\(_3\) from NH\(_4^+\)

 

 

 

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

Fe\(^{3+}\) present 

 

 

Cl\(^-\) or CO\(_3^{2-}\)

Cl\(^-\) present 

 


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WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC offline past questions - with all answers and explanations in one app - Download for free
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 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