Question 1
WAEC
•
2022
•
CHEMISTRY
•
practical
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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About This Question
This is
Waec
2022
Chemistry
Question 1.
It is one of the
practical
questions from the
2022
Waec
Chemistry
examination.
The question covers
General
.