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GCSE Chemistry AQA > C8 Chemical analysis > Flashcards

C8 Chemical analysis Flashcards

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1
Q

What is a pure substance?

A

a substance with only 1 element/compound throughout

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2
Q

How can we test how pure a substance is?

A

we can compare MP/BP and the closer to the actual value, the purer it it.

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3
Q

What is the effect of impurities on the melting point?

A

impurities lower the melting point

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4
Q

What is the effect of impurities on the boiling point?

A

impurities increase the boiling point of a sample

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5
Q

what are formulations?

A

useful mixtures made of exact amounts of components

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6
Q

What is in the formulation of paint?

A

pigment
solvent
binder
additives

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7
Q

Why are formulations useful in the pharmacutical industry?

A

so chemists can ensure drugs are delivered to the correct part of the body, at the right concentration and has a long shelf life

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8
Q

What is chromatography?

A

a method to seperate the substances of a mixture

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9
Q

what are the 2 phases in chromatography?

A

a mobile phase

a stationary phase

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10
Q

how do you calculate the Rf value from chromatography?

A

distance travelled by solvent

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11
Q

What has to be done to make chromatography useful?

A

test a pure substance next to it so you can compare

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12
Q

What is the test for chlorine?

A

bleeches damp litmus paper white

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13
Q

What is the test for oxygen?

A

ignites a glowing splint

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14
Q

What is the test for carbon dioxide?

A

turns lime water (calcium hydroxide) cloudy

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15
Q

What si the test for hydrogen?

A

makes a squeaky pop when ignited with a lit splint

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16
Q

What are the 3 test for anions?

A

dilute acid-to test for carbonates
barium chloride and HCL- can test for sulphates
nitric acid and silver nitrate can test for halides

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17
Q

How can you test for carbonates?

A

add dilute acid and see if it turns limewater cloudy as co2 is released

18
Q

How can you test for sulfates?

A

add a few drops on HCL and a few drops of barium chloride. a white precipitate will form if sulfate ions are present

19
Q

How can you test for halides

A

add a few drops of nitric acid and silver nitrate.

the colour of precipitate determines the halide ion

20
Q

In a halide ion test, what precipitates do chloride ions form?

A

white

21
Q

In a halide ion test, what precipitates do bromide ions form?

A

cream

22
Q

In a halide ion test, what precipitates do iodide ions form?

A

yellow

23
Q

What colour flame to lithium ions burn with?

A

crimson

24
Q

What colour flame to sodium ions burn with?

A

yellow

25
Q

What colour flame to potassium ions burn with?

A

lilac

26
Q

What colour flame to calcium ions burn with?

A

orange-red

27
Q

What colour flame to copper ions burn with?

A

green

28
Q

Why do you clean the loop in HCL in flame tests?

A

to ensure the loop isnt contaminated

29
Q

What is a disadvantage of flame tests?

A

you can only detect samples that contain a single metal ion and not a mixture

30
Q

what 2 ways can you test for cations?

A

flame tests

adding NaOH

31
Q

What colour precipitate does calcium form when NaOH is added?

A

white

32
Q

What colour precipitate does copper form when NaOH is added?

A

blue

33
Q

What colour precipitate does iron(II) form when NaOH is added?

A

green

34
Q

What colour precipitate does iron (III) form when NaOH is added?

A

brown

35
Q

What colour precipitate does magnesium form when NaOH is added?

A

white

36
Q

What colour precipitate does aluminium form when NaOH is added?

A

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

37
Q

What is flame emission spectroscopy?

A

when a sample is placed in a flame. as the ions heat up, their electrons become excited. when they then drop down to their original energy level, they transfer energy as light which can pass through a stechoscope ad detect different wavelengths of light

38
Q

What does the combination of a wavelength emitted by an ion?

A

is charge and electron arrangement.

39
Q

What can flame emission spectroscopy be used for?

A

identifying ions in solutions and calculating concentrations

40
Q

Why are machines used for analysing unknown substances (instrumental analysis)?

A

very sensitive
very fast
very accurate

41
Q

Does flame emission spectroscopy work for mixtures?

A

yes- this is why its more useful than flame tests

GCSE Chemistry AQA (11 decks)

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