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*Chemistry: Experiments > Q1. *Iodine-thiosulfate titration > Flashcards

Q1. *Iodine-thiosulfate titration Flashcards

1
Q

List the chemicals required in this experiment.

6

A

Sodium thiosulfate crystals

Potassium permanganate solution (0.02 M)

Dilute sulfuric acid (1M)

Potassium iodide solution (o.5 M)

Starch indicator

Deionised water

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2
Q

What Molar potassium permanganate solution is used?

A

0.02 M

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3
Q

What Molar potassium iodide solution is used?

A

0.5 M

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4
Q

What is the first step in this experiment?

A

Weigh out on a clock glass about 6.25g sodium thiosulfate crystals

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5
Q

How much sodium thiosulfate crystals should be used?

A

About 6.25g

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6
Q

What should be used to weigh the sodium thiosulfate crystals?

A

A clock glass

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7
Q

What is the second step in this experiment, sodium thiosulfate crystals have been measured?

A

Transfer the crystals to a beaker containing approximately 100 cm cubed of deionised water

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8
Q

What should the sodium thiosulfate crystals be transferred to?

A

A beaker containing 100 cm cubed

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9
Q

What should be transferred to the beaker containing 100 cm cubed of deionised water?

A

The sodium thiosulfate crystals

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10
Q

What is the third step of this experiment, the sodium thiosulfate crystals have just been added to a beaker of water?
(2)

A

Stir to dissolve the crystals

When dissolved transfer the solution to a clean 250 cm cubed volumetric flask

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11
Q

When the crystals have been dissolved in the water where should it be transferred to?

A

A clean 250 cm cubed volumetric flask

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12
Q

What is the fourth step of this experiment, the solution containing the crystals has been transferred to a volumetric flask?
(2)

A

Transfer all the washings to the volumetric flask and make up to the mark with deionised water

Invert the stoppered flask about 20 times

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13
Q

What should be transferred to the volumetric flask along with the solution of dissolved crystals?

A

All the washings from the beaker

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14
Q

What should you use to make the volumetric flask up to the mark?

A

You should use deionised water

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15
Q

How many times should you invert the volumetric flask?

A

About 20 times

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16
Q

What is the fifth step of the experiment, the volumetric flask has just been filled to the mark with deionised water?

A

Wash out the pipette, burette and conical flask with deionised water

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17
Q

What pieces of equipment should be washed out with deionised water?
(3)

A

Pipette

Burette

Conical flask

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18
Q

What should the pipette, burette and conical flask be washed out with?

A

They should be washed out with deionised water

19
Q

What is the sixth step of the experiment, the equipment has been washed with deionised water?
(6)

A

Wash out the burette with some of the sodium thiosulfate solution

Fill burette above the zero mark with the solution

Remove the funnel from the burette

The bottom of the meniscus is adjusted to the level of the solution to the zero mark

Ensure that the tap and space below the tap are also filled

20
Q

What piece of equipment should be rinsed with the sodium thiosulfate solution?

A

The burette

21
Q

What should the burette be rinsed with?

A

Sodium thiosulfate solution

22
Q

List the four steps that should be followed when filling the burette.

A

Fill burette above the zero mark with the solution

Remove the funnel from the burette

The bottom of the meniscus is adjusted to the level of the solution to the zero mark

Ensure that the tap and space below the tap are also filled

23
Q

What is the seventh step in this experiment, the burette has just been filled?
(3)

A

Pour approximately 100 cm cubed of standardised KMnO4 solution into a clean, dry beaker

Wash out the pipette with a small amount of this solution

Using a pipette filler, pipette 25 cm cubed of the solution into the conical flask

24
Q

How much of the standardised KMnO4 should be poured into a beaker?

A

100 cm cubed

25
Q

100 cubed of what should be poured into a clean, dry beaker?

A

100 cubed of standardised KMnO4

26
Q

What should be washed out with standardised KMnO4?

27
Q

What should the pipette be washed out with?

A

Standardised KMnO4

28
Q

How much of the standardised KMnO4 should be pipetted into a conical flask?

A

25 cm cubed

29
Q

Where should 25 cm cubed of standardised KMnO4 be pipetted to?

A

Into a conical flask

30
Q

What is the eight step of this experiment, the conical flask has been filled with 25 cm cubed a standardised KMnO4?
(2)

A

Using a graduated cylinder and approximately 2o cm cubed of dilute sulfuric acid followed by 10 cm cubed of 0.5 M potassium iodide solution to the conical flask

Note the reddish-brown colour of the liberated iodine

31
Q

What colour is the solution in the conical flask before the potassium iodide solution is added?

32
Q

Why is sulfuric acid added to the conical flask in excess?

A

The sulfuric acid is added in excess to the potassium permanganate solution in the conical flaks in order to supply sufficient H+ ions for complete reduction of the MnO4- ions to Mn2+ ions

33
Q

What substances are added to the conical flask?

2

A

Dilute sulfuric acid

0.5 M potassium iodide solution

34
Q

How much dilute sulfuric acid is added to the conical flask?

A

20 cm cubed

35
Q

How much 0.5M potassium iodide solution is added to the conical flask?

A

10 cm cubed

36
Q

What colour is the solution after the 0.5 M potassium iodide solution?

A

The solution turns reddish-brown

37
Q

What is the ninth step of the experiment, the solution in the conical flask is now reddish-brown?
(2)

A

Titrate in the usual manner until the solution in the conical flask becomes pale yellow

Now add a few drops of starch indicator until a blue/black colour is observed

38
Q

When should the starch indicator be added?

A

When the solution in the conical flask becomes pale yellow

39
Q

What colour does the solution become when the starch indicator is added?

A

Turns from pale yellow to blue/black

40
Q

What is the tenth step of the experiment, the solution is not blue/black?
(2)

A

Continue the titration, adding the thiosulfate solution drop by drop, until the blue/black colour disappears

Note the titration figure

41
Q

How do you know the end point has been reached?

A

The blue/black colour disappears

42
Q

What is the eleventh step of the experiment, the solution is now colourless?
(3)

A

Perform one rough and two accurate titrations

The two accurate titration figures should agree to within 0.1cm cubed

Using the results of this experiment, work out the concentration of the sodium thiosulfate solution

43
Q

How many titrations should be carried out?

A

Perform one rough and two accurate titrations

44
Q

The two accurate figures to agree to within what measurement?

A

0.1 cm cubed

*Chemistry: Experiments (15 decks)

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