Page 405 - SUBSEC October 2017_Neat

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Answer ALL questions.

1. You are provided with TWO solutions:

(i) a solution of ammonium iron (II) sulphate hexahydrate, (NH ) SO FeSO 6H O containing
4 2
4
2
4
39.00g of the salt in 1dm of solution labelled R.
3
(ii) a solution of potassium manganate(VII), KMnO , labelled S. DO NOT WRITE IN THIS AREA
4
The ionic equation for the reaction is
5Fe (aq) + MnO (aq) + 8H (aq) → 5Fe (aq) + Mn (aq) + 4H O (l).
2+−
+
2+
3+
4− 2
Carry out the following procedure to determine the concentration for potassium manganate (VII)
solution S.
The results are to be entered into Table 1.
(a) Procedure
A. Pipette 25 cm of the solution R into a clean conical flask.
3
B. Add an approximately equal volume of dilute sulphuric acid to the conical flask.
C. Fill the burette with the solution S.
D. Titrate the mixture of R with the solution S.
E. Record both your initial burette reading and reading at the end point to two
decimal places.
F. Repeat steps A-E until consistent results are obtained. DO NOT WRITE IN THIS AREA

TABLE 1: DATA FOR EXPERIMENTAL PROCEDURE

1 2 3

Final burette reading (cm )
3
Initial burette reading (cm )
3
Volume of KMnO used (cm )
3
4
[6 marks]

(b) Describe the colour of the mixture at the end point of the titration.
.............................................................................................................................................

.............................................................................................................................................
[1 mark] DO NOT WRITE IN THIS AREA
(c) Calculate the volume of KMnO used for the titration.
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[1 mark]
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