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Chemistry > Topic 8: Chemical Analysis > Flashcards

Topic 8: Chemical Analysis Flashcards

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1
Q

In chemistry, what is a pure substance?

A

Something that contains only one type of compound or element

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2
Q

What is true of the melting and boiling points of a chemically pure substance?

A

It will melt and boil at a specific temperature

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3
Q

How could you identify the purity of a sample? [2]

A
  1. Measure its melting and boiling point and compare it with that of a pure substance (in a data book)
  2. The closer the measured value is to the actual melting or boiling point, the purer your sample is
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4
Q

What is true of an impure sample? [3]

A
  1. Will melt and boil over a range of temperatures
  2. Melting point will decrease
  3. Boiling point will increase
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5
Q

What is a formulation? [2]

A

A useful mixture with a precise purpose [1] which’s components have been measured carefully to ensure it meets its required function [1]

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6
Q

Examples of formulations in everyday life [4]

A
  1. Cleaning products
  2. Paints
  3. Medicines
  4. Fertilisers
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7
Q

What is chromatography used to do?

A

Used to separate the substances in a mixture

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8
Q

What does the ‘mobile phase’ mean in chromatography?

A

Where the molecules can move (solvent)

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9
Q

What does the ‘stationary phase’ mean in chromatography?

A

Where the molecules can’t move (paper)

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10
Q

A chemical that travels further up the paper has spent how much time in each phase?

A

Longer in the mobile phase than stationary phase

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11
Q

How many spots will a pure substance make in chromatography?

A

1

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12
Q

In chromatogarphy, the time a chemical spends in each phase depends on what 2 things?

A
  1. How soluble it is in the solvent
  2. How attracted to the paper it is
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13
Q

How do you calculate Rf value?

A

Distance travelled by substance/distance travelled by solvent

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14
Q

Describe the test for chlorine [2]

A
  1. Equipment needed is damp litmus paper
  2. If chlorine is present, paper will be bleached white
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15
Q

Describe the test for oxygen [2]

A
  1. Equipment needed is a glowing splint
  2. If oxygen is present, the splint will re-ignite
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16
Q

Describe the test for hydrogen [2]

A
  1. Equipment needed is a burning splint
  2. If hydrogen is present, you will hear a squeaky pop
17
Q

Describe the test for carbon dioxide [2]

A
  1. Equipment needed is limewater
  2. If carbon dioxide is present, limewater will turn cloudy
18
Q

Describe how you would test for carbonate ions [3]

A
  1. Put the sample in a test tube and add some dilute acid
  2. Connect the test tube to a test tube of limewater
  3. If carbonate ions are present, carbon dioxide will be released that will turn the limewater cloudy
19
Q

Describe how you would test for sulfate ions [2]

A
  1. Add dilute hydrochloric acid and barium chloride to a test tube containing you mystery solution
  2. If sulfate ions are present, a white precipitate of barium sulfate will form
20
Q

Why is hydrochloric acid added when testing for sulfate ions?

A

To get rid of any traces of carbonate ions - these would also produce a white precipitate which would confuse the results

21
Q

Describe how you would test for halide ions

A

Add dilute nitric acid and silver nitrate solution to your mystery solution

22
Q

What colour is silver chloride?

A

White

23
Q

What colour is silver bromide?

A

Cream

24
Q

What colour is silver iodide?

A

Yellow

25
Q

Lithium - flame colour?

A

Crimson

26
Q

Sodium - flame colour?

A

Yellow

27
Q

Potassium - flame colour?

A

Lilac

28
Q

Calcium - flame colour?

A

Orange-red

29
Q

Copper - flame colour?

A

Green

30
Q

Calcium - colour of precipitate?

A

White

31
Q

Copper (II) - colour of precipitate?

A

Blue

32
Q

Iron (II) - colour of precipitate?

A

Green

33
Q

Iron (III) - colour of precipitate?

A

Brown

34
Q

Aluminium - colour of precipitate?

A

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

35
Q

Magnesium - colour of precipitate?

A

White

36
Q

Describe how flame emission spectroscopy can be used [4]

A
  1. The sample is put into a flame
  2. The light given out is put through a spectroscope
  3. The output is a line spectrum
  4. This can be analysed to identify the metal ions present and their concentrations
37
Q

Why might it be necessary to use flame emission spectroscopy instead of a flame test to identify metal ions? [2]

A

Flame emission spectroscopy can be used to identify the metal ions in mixtures [1] whereas flame tests can only be used for substances that contain a single metal ion [1]

38
Q

What are the advantages of using intrumental methods vs conducting tests? [3]

A
  1. More sensitive
  2. Faster - don’t need a human
  3. More accurate

Chemistry (10 decks)

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