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5070 s10 ir 31.pdf


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© UCLES 2010

P

Q

[H]

[H]

0.1 mol/dm3 hydrochloric acid

150 cm3

methyl orange or screened
methyl orange indicator

0.1 mol/dm3 sodium hydroxide

identity

150 cm3

per
candidate
4.0 g/dm3 sodium hydroxide

notes

5070/31/CI/M/J/10

approximately 0.1 mol/dm3
potassium chromate(VI)

10 cm3

T

approximately 0.1 mol/dm3
potassium iodide

10 cm3

S

19.4 g of potassium chromate(VI) [T] [N] in 1 dm3 of distilled water

16.6 g of potassium iodide in 1 dm3 of distilled water

10.6 g of anhydrous sodium carbonate [H] in 1 dm3 of distilled water

label

aqueous hydrogen peroxide

hazard

[H]

‘20 volume’ hydrogen peroxide
solution

identity

notes

If necessary the following reagent may be made available from a communal supply; however, the attention of the Invigilators should be drawn to the fact
that such an arrangement may enhance the opportunity for malpractice between candidates.

[T] [N]

approximately 0.1 mol/dm3
sodium carbonate

10 cm3

R

Supervisors are asked to carry out a standard acid/base titration between solutions Q and P to ensure that the concentrations of the two solutions
fall within the given range. It is essential that 25.0 cm3 of P reacts with between 24.0 cm3 and 26.0 cm3 of Q (or 20.0 cm3 of P reacts with between
19.0 cm3 and 21.0 cm3 of Q.

[T]

label

Particular requirements

2

hazard

It is especially important that great care is taken that the confidential information given below does not reach the candidates either directly or
indirectly.

1

Chemicals Required

4