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Chemistry Paper 2 > 8-Chemical Analysis > Flashcards

8-Chemical Analysis Flashcards

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1
Q

What is purity defined as in chemistry

A

A pure substance only contains one compound or element and is not mixed with anything else

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2
Q

How can u test the purity of a substance

A

Measure its melting or boiling point and compare it the melting or boiling point of the pure substance.
The closer it is to the actual m.p or b.p the pure pure it is

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3
Q

What will impurities do to the melting point of the substance

A

It will lower the melting point and increase the melting range of the substance

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4
Q

What will impurities do to the boiling point of a substance

A

They will increase the boiling point and it may result in the substance boiling at a range of temperatures

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5
Q

What is a formulation

A

Useful mixtures with a precise purpose that are made by following a formula

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6
Q

What are examples of formulations

A 
Found in:
Cleaning products 
Fuels
Cosmetics
Fertilisers
Metal alloys
Food and drink
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7
Q

What is the mobile phase

A

Where the molecules can move. This is always a liquid or a gas

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8
Q

What is the stationary phase

A

Where the molecules can’t move.

This can be a solid or a really thick liquid

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9
Q

What is the stationary phase in paper chromatography

A

The filter paper

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10
Q

What is the mobile phase in paper chromatography

A

The solvent - water or ethanol

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11
Q

What does the amount of time spent in each phase depend on

A

How soluble they are in the solvent,

How attracted they are to the paper

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12
Q

What happens to molecules that have a higher solubility

A

They spend more time in the mobile phase and are carried further up the paper

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13
Q

What is a chromatogram

A

The result of the chromatography analysis on the paper

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14
Q

How do u calculate Rf value

A

Rf = distance travelled by substance(B) / distance travelled by solvent(A)

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15
Q

How many spots will be on the chromatogram if the substance is pure

A

1

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16
Q

What is the test for chlorine

A

It bleaches damp litmus paper white

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17
Q

What is the test for oxygen

A

It will relight a glowing splint

18
Q

What is the test for carbon dioxide

A

Bubbling CO2 through an aqueous solution of calcium hydroxide (lime water) will turn it cloudy

19
Q

What is the test for hydrogen

A

If u hold a lit splint at the open end of a test tube containing hydrogen, you’ll get a squeaky pop

20
Q

How do u test for carbonates

A

Add dilute acid to the sample,
Connect test tube to some lime water,
If lime water goes cloudy then carbonate is present

21
Q

How do you test for sultates

A

Add a couple drops of dilute hydrochloric acid and a couple of drops of barium chloride solution to the sample.
If sulfate ions are present, a white precipitate is formed

22
Q

How do u test for Halides

A

Add a couple drops of dilute nitric acid and a couple drops of silver nitrate solution to the sample

23
Q

What do chloride, bromide and iodide produce in the halide test

A

Chloride- white precipitate of silver bromide
Bromide- cream precipitate of silver bromide
Iodide- yellow precipitate of silver iodide

24
Q

What colour flame do lithium ions produce

A

Crimson

25
Q

What colour flame do sodium ions produce

A

Yellow

26
Q

What colour flame do potassium ions produce

A

Lilac

27
Q

What colour flame do calcium ions produce

A

Orange-red

28
Q

What colour flame do copper ions produce

A

Green

29
Q

How do prepare for a flame test

A

Clean a platinum wire loop by dipping it some dilute HCL and then hold in blue flame until it burns without any colour

30
Q

How do u carry out a flame test

A

Dip titanium loop into sample and put it in the flame.

Record the colour of the flame

31
Q

How do u test for metals

A

Add a few drops of sodium hydroxide solution to the sample.

If metal present, it forms an insoluble hydroxide

32
Q

What colour precipitate does calcium produce when sodium hydroxide is added

A

White

33
Q

What colour precipitate does copper(II) produce when sodium hydroxide is added

A

Blue

34
Q

What colour precipitate does iron (II) produce when sodium hydroxide is added

A

Green

35
Q

What colour precipitate does iron(III) produce when sodium hydroxide is added

A

Brown

36
Q

What colour precipitate does aluminium produce when sodium hydroxide is added

A

White at first but then redissolves in excess NaOH to form a colourless solution

37
Q

What colour precipitate does magnesium produce when sodium hydroxide is added

A

White

38
Q

Explain how a coloured flame is produced

A

As the ions heat up, their electrons become excited. When the electrons drop back to their original energy levels, they transfer energy as light

39
Q

What is a spectroscope

A

As light passes through it, it can detect different wavelengths of light to produce a line spectrum

40
Q

What does the intensity of the spectrum show

A

Shows the concentration of that ion in the solution

41
Q

What are the advantages of instrumental analysis (tests that use machines)

A

Very sensitive
Very fast
Very accurate

Chemistry Paper 2 (5 decks)

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