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Chemistry 9-1 iGCSE Oxford AQA > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

1
Q

What is test for chlorine?

A

Chlorine bleaches damp litmus paper = turns it white

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2
Q

If you use blue litmus paper (when testing for chlorine), why might it turn red for a moment?

A

Because solution of chlorine is acidic

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3
Q

What smell does chlorine have?

A

Has characteristic sharp, choking smell

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4
Q

What is test for hydrogen?

A

Burning splint at open end of test tube containing hydrogen = get “squeaky pop”

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5
Q

Where does the noise come from when testing for hydrogen?

A

Comes from hydrogen burning quickly in oxygen in air to form water

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6
Q

What is the test for oxygen?

A

Glowing splint inside test tube containing oxygen = oxygen will relight growling splint

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7
Q

What is the test for carbon dioxide?

A

Bubbling carbon dioxide though limewater = solution turns cloudy

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8
Q

What is test for ammonia?

A
  • Makes damp red litmus paper turn blue
  • Forms a white smoke of ammonium chloride when hydrogen chloride gas (from concentrated hydrochloric acid) is held near it
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9
Q

What is the test for sulfate ions?

A
  1. Use dropping pipette to add a couple drops of dilute hydrochloric acid (HCl)
  2. Followed by couple drops of barium chloride solution (BaCl2) to test tube containing mystery solution
  3. If sulfate ions are present = white precipitate of barium sulfate will form
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10
Q

What is the test carbonate ions?

A
  1. Using a dropping pipette to add few drops of dilute acid to test tube containing mystery substance
  2. Then connect test tube to test tube containing limewater
  3. If carbonate ions are present = reaction with acid will release CO2 = turns limewater cloudy when it bubbles through
  4. Turns cloudy white bc carbon dioxide produces = a white precipitate
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11
Q

What is the test for halide ions (Cl-, Br-, I-)?

A
  1. Add couple drops of dilute nitric acid (HNO3)
  2. Followed by couple drops of silver nitrate solution (AgNO3) to mystery solution
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12
Q

In the test for halide ions, what does chloride give?

A

White precipitate of silver chloride

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13
Q

In the test for halide ions, what does bromide give?

A

Cream precipitate of silver bromide

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14
Q

In the test for halide ions, what does iodide give?

A

Yellow predicate of silver iodide

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15
Q

How can you test for metal ions?

A

By heating your substance and seeing whether the flame turns a distinctive colour → use these colours to detect & identify different ions

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16
Q

Describe the method for testing for metal ions

A
  1. Clean nichrome or platinum wire loop by rubbing with fine emery paper
  2. Hold it in blue flame Bunsen burner
  3. Flame might change colour but once it’s blue again = loop is clean
  4. Dip loop into sample you want to test & put back in flame
  5. Record colour of flame
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17
Q

Why does the method for testing for metal ions only work for samples that contain a single metal ion?

A

If sample tested contains a mixture of metal ions = flame colours of some ions may be hidden by colours of others

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18
Q

What colour flame do lithium ions produce?

A

Crimson

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19
Q

What colour flame do sodium ions produce?

A

Yellow

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20
Q

What colour flame do potassium ions produce?

A

Lilac

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21
Q

What colour flame do calcium ions produce?

A

Orange-Red

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22
Q

Many metal hydroxides are…

A

Insoluble and precipitate out of solution when formed

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23
Q

What is the test for (some) metals?

A
  1. Add few drops of sodium hydroxide solution to a solution of your mystery compound
  2. If you get a coloured precipitate (insoluble hydroxide) = can tell which metal was in the compound
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24
Q

What is the colour of the precipitate that calcium ions forms?

A

White

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25
Q

What is the colour of the precipitate that copper(II) ions forms?

A

Blue

26
Q

What is the colour of the precipitate that iron(II) ions forms?

A

Green

27
Q

What is the colour of the precipitate that iron(III) ions forms?

A

Brown

28
Q

What is the colour of the precipitate that aluminium ions forms?

A

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

29
Q

What is the colour of the precipitate that magnesium ions forms?

A

White

30
Q

What colour flame do barium ions produce?

A

Green

31
Q

What is a pure substance?

A

Substance that contains only one compound or element throughout

32
Q

A chemically pure substance will melt or boil at a…

A

specific temperature

33
Q

How can you test the purity of sample?

A

By measuring its melting/boiling point & comparing it with melting/boiling point of pure substance

34
Q

The purer the sample, the…

A

closer its melting/boiling point is to the actual melting/boiling point (of the pure substance)

35
Q

What will impurities in sample do to the melting point? (name 2 things)

A
  1. Lower the melting point
  2. Increase melting range of substance
36
Q

What will impurities in sample do to the boiling point? (name 2 things)

A
  1. Increase the boiling point
  2. Sample boils at range of temperatures
37
Q

What are formulations?

A

Useful mixtures with a precise purpose that are made by following a ‘formula’ (i.e. a recipe)

38
Q

In a formulation, what is each component and what do they do (and why)?

A

Each component: measured quantity & contributes to properties → to meets its required function

39
Q

Name 3 products that formulations are found in

A
  1. Cosmetics
  2. Cleaning products
  3. Fuels
  4. Metal Alloys
  5. Drugs
  6. Fertilisers
40
Q

Explain how paint is a formulation

A

It’s composed of pigments, solvents, binders, additives, etc

Depending on purpose of paint = chemicals used and their amounts will be changed so paint produced is right for the job

41
Q

What is chromatography?

A

(Analytical) method used to separate substances in a mixture (based on their solubilities) & then used to identify substances

42
Q

Name the 2 phases in chromatography

A
  1. Mobile Phase
  2. Stationary Phase
43
Q

A mobile phase is where…

A

Where molecules can move

44
Q

A stationary phase is where…

A

where molecules can’t move

45
Q

Where does the mobile phase take place?

A

Always in liquid or gas

46
Q

Where does the stationary phase take place?

A

Solid or really thick liquid

47
Q

During chromatography, what do substances in a sample do constantly?

A

Constantly move between mobile and stationary phrases

48
Q

What is formed when substances in a sample constantly move between mobile and stationary phases?

A

Equilibrium (formed between 2 phases)

49
Q

When the mobile phase moves through stationary phase, what happens?

A

Anything dissolved in mobile phase moves with it

50
Q

How quickly a chemical moves between the 2 phases depends on…

A

how it’s ‘distributed’ i.e. whether it spends more time in mobile phase or stationary phase

51
Q

What happens to chemicals that spend more time in mobile phase than stationary phase?

A

They will move further through the stationary phase

52
Q

When do components in mixture normally separate?

A

Through stationary phase BUT only if all components spend different amounts of time in mobile phase

53
Q

Why may the number of spots change in different solvents?

A

Bc the distribution of a chemical may change depending on solvent

54
Q

How do you know a substance is pure in chromatography?

A

When it forms one spot in any solvent

55
Q

Why does a pure substance only form one spot in chromatography?

A

Bc there’s only one substance in sample

56
Q

How do you work out a Rf value?

A

Distance travelled by substance (B)

Distance travelled by solvent (A)

57
Q

In paper chromatography, what is the stationary phase?

A

The chromatography paper (filter paper)

58
Q

In paper chromatography, what is the mobile phase?

A

Solvent

59
Q

In paper chromatography, the amount of time molecules spend in each phase depends on what? (name 2 things)

A
  • How souble they are in a solvent
  • How attracted they are to the paper
60
Q

Why will molecules with a higher solubility in a solvent be carried further up the paper?

A

They’re more attracted to the mobile stage/solvent (i.e. spend more time in the mobile phase)

61
Q

Why will molecules with a low solubility (in a solvent) travel not very far up the paper?

A

They’re more attracted to the stationary stage/paper (i.e. spend more time in the stationary phase)

62
Q

In chromatography, what does separation depend on?

A

Amount of time substances spend in mobile and stationary phase

Chemistry 9-1 iGCSE Oxford AQA (11 decks)

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