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Chemistry extension edexcel > C3.1 Qualitative analysis > Flashcards

C3.1 Qualitative analysis Flashcards

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1
Q

What are two reasons chemical analysis is used on food and other products?

A

Purity and safety

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2
Q

What are the two main types of chemical analysis?

A

Qualitative and quantitative analysis

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3
Q

What is qualitative analysis used for?

A

Investigating what kind of substances are present in a sample

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4
Q

What is quantitative analysis used for?

A

Measuring the amount of each substance present in a sample

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5
Q

What two things must an analyst identify to identify the ionic compound?

A

The anion and cation

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6
Q

How can you be sure that the answer is correct when using an ion test?

A

The ion test must give a positive result to only one type of ion

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7
Q

What can flame tests be used for?

A

Detecting some metal cations

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8
Q

What colour flame does the flame test for calcium produce?

A

Brick red

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9
Q

What colour flame does the flame test for sodium produce?

A

Yellow

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10
Q

What colour flame does the flame test for potassium produce?

A

Lilac

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11
Q

What colour flame does the flame test for copper produce?

A

Green/blue

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12
Q

How are cations that can’t be detected with a flame test identified?

A

By adding a few drops of sodium hydroxide solution

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13
Q

Why does adding a few drops of sodium hydroxide solution to an unknown substance help identify a cation?

A

Because many metal hydroxides are insoluble, so a precipitation reaction can occur. The precipitate formed can then be used to identify the ion present

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14
Q

What colour precipitate does a cation of aluminium form when sodium hydroxide solution is added to it?

A

White

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15
Q

What colour precipitate does a cation of calcium form when sodium hydroxide solution is added to it?

A

White

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16
Q

What colour precipitate does a cation of copper(||) form when sodium hydroxide solution is added to it?

A

Pale blue

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17
Q

What colour precipitate does a cation of iron(||) form when sodium hydroxide is added to it?

A

Green

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18
Q

What colour precipitate does a cation of iron(|||) form when sodium hydroxide solution is added to it?

A

Brown (rust)

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19
Q

How can you distinguish calcium and aluminium ions when they both form a white precipitate when a few drops of sodium hydroxide solution is added to them?

A

You add sodium hydroxide in excess

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20
Q

What happens to the white calcium ion precipitate when sodium hydroxide solution is added in excess?

A

It remains unchanged

21
Q

What happens to the white aluminium ion precipitate when sodium hydroxide solution is added in excess?

A

The precipitate redissolves to form a colourless solution

22
Q

What is the precipitate when adding sodium hydroxide solution to an unknown substance?

A

A solid hydroxide of the cation

23
Q

What would the precipitate formed from the reaction of copper(||) sulphate and sodium hydroxide be?

A

Copper(||) hydroxide

24
Q

Why must an ion test only give a positive result for one type of ion?

A

If a positive result was produced for two or more different ions you wouldn’t be sure which of these ions was present in the compound

25
Q

What are the three ways the water supply in Britain is cleaned?

A
  • filtered to remove solid particles
  • chlorinated to kill bacteria
  • chemically treated to remove other impurities
26
Q

What group is chlorine found in?

A

Group 7 (halogens)

27
Q

How can halide ions be identified?

A

By acidifying the solution with dilute nitric acid, then adding silver nitrate

28
Q

What precipitate is produced when dilute nitric acid and silver nitrate are added to a solution containing halides?

A

A silver halide precipitate

29
Q

What colour precipitate is formed when silver nitrate is added to an acidified solution containing chloride ions?

A

White

30
Q

What colour precipitate is formed when silver nitrate is added to an acidified solution containing bromide ions?

A

Cream

31
Q

What colour precipitate is formed when silver nitrate is added to an acidified solution containing iodide ions?

A

Yellow

32
Q

Why can ions in solution move about independently?

A

Because they are separated

33
Q

What ions do many types of fertiliser contain?

A

Ammonium ions

34
Q

Why can fertilisers be dangerous?

A

They can get into rivers and lakes and harm water life

35
Q

How do you test for ammonium ions?

A

The substance is warmed with sodium hydroxide solution. If a smelly alkaline gas is given off that turns damp red litmus paper blue it is ammonia gas

36
Q

How is a carbonate identified?

A

You add a dilute acid to the substance. If the gas given off turns limewater milky it is carbon dioxide gas and so the substance was a carbonate

37
Q

How does water get dissolved substances inside it?

A
  • from the rocks over which it flows

- from the chemicals used in water treatment

38
Q

Why are maximum limits for the amounts of chemicals and microorganism found in water set?

A
  • so that it looks and tastes good

- so that it’s safe to drink

39
Q

What are three chemicals used in water treatment?

A
  • chlorine
  • aluminium salts
  • sodium fluoride
40
Q

Why is sodium fluoride added during water treatment?

A

It has been shown to reduce tooth decay

41
Q

Why are aluminium salts added during water treatment?

A

To remove small particles of solids

42
Q

Why are some scientists concerned about the use aluminium fluoride within water treatment?

A

High levels of aluminium have been linked to Alzheimer’s disease and damage to the digestive system

43
Q

How do aluminium salts remove small particles of solids from water?

A

They stick to small dirt particles to form clumps so that they can be removed more easily

44
Q

What is a pure liquid?

A

A liquid that only contains one substance

45
Q

What does an acid + a metal produce?

A

A salt + hydrogen

45
Q

What does an acid + a base produce?

A

A salt + water

45
Q

What does an acid + a metal oxide produce?

A

A salt + water

45
Q

What does an acid + a metal carbonate produce?

A

A salt + water + carbon dioxide

Chemistry extension edexcel (5 decks)

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