WAEC 2022 Chemistry | Practical

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Question 1 View Details
Question Parts
(a)
A is an aqueous solution of Iodine. B is 0.100 mol dm-3 sodium trioxothiosulphate (II). Put B into the burette. Pipette 20.0 cm³ or 25.0 cm³ of A into a conical flask. Add from the burette until the reddish-brown colour fades to pale yellow, then add a few drops of starch indicator to obtain a dark blue solution. Continue adding B slowly from the burette until one drop of B causes the blue colour to disappear, leaving a colourless solution. Repeat the titration to obtain concordant titre values. Tabulate your results and calculate the average volume of B used. The equation for the reaction is: 2 Na_{2} S_{2} O_{3(aq)} + I_{2(aq)} \rightarrow Na_{2} S_{2} O_{6(aq)} + 2 NaI_{(aq)}
(b)
From your results and the information provided, calculate the: i. Concentration in mol dm-3 of iodine in A; ii. mass in grammes of iodine in 1.00 dm³ of A. [I=127.0]
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Question 2 View Details
Question Parts
(a)
C contains two cations and one anion. Dissolve all of C in about 10 cm³ of distilled water. Carry out the following exercise on portions of the resulting solution: i. To about 2 cm³ of the solution, add NaOH(aq) in drops then in excess. Warm gently the resulting mixture. ii. To about 2 cm³ of the solution, add BaCl₂(aq) followed by excess dilute HCl.
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Question 3 View Details
Question Parts
(a)
Describe one chemical test to distinguish between carbon (IV) oxide and sulphur (IV) oxide.
(b)
(i) State the laboratory method of collection of each of the following gases: (1) H₂; (II) NH₃; (III) HCl.
(b)
(ii) Give a reason for each of the answers stated in 3(b)(i).
(c)
State the method used in separating each of the following mixtures: i. two miscible liquids; ii. soluble salt and insoluble salt.
(d)
Explain briefly why a solution of KCl does not give off a gas when mixed with NaHCO₃ solution, but a solution of AlCl₃ does.
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