23.2 - Manganate (VII) redox titrations Flashcards Preview

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Flashcards in 23.2 - Manganate (VII) redox titrations Deck (11):
1

Describe how you would set up a manganate (VII) titration

1) Standard solution of KMnO4 added to burette
2) Add measured volume of solution being analysed to conical flask
3) Add an excess of H2SO4

2

What do you add to the burette in manganate (VII) titrations?

Standard solution of KMnO4

3

Why is H2SO4 added to the conical flask in manganate (VII) titrations?

To provide the H+ ions required for the reduction of MnO4- ions

4

Is an indicator used in manganate (VII) titrations? Why?

No
The reaction is self-indicating

5

What is the colour that indicates the end point of the manganate (VII) titration?

Permanent pale pink colour

6

What does a permanent pink colour indicate?

Indicates that there is an excess of MnO4- ions present

7

What is the colour change involved in manganate (VII) titrations?

Purple --> pale pink

8

Why is the top of the meniscus recorded, not the bottom?

Because KMnO4 is a deep purple colour so it is difficult to see the bottom of the meniscus through the intense colour

9

Which titres are used when calculating the mean?

2 concordant titres

10

Titre = 22.30 cm3
Each burette reading had an uncertainty of 0.05%

Calculate the % uncertainty

0.05 x 2 / 22.30

x100

= 0.45%

11

What happens to the MnO4- ions during a manganate (VII) redox titration? What does this suggest?

MnO4- ions are reduced
Suggests that the other chemical used is a reducing agent, which becomes oxidised