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GCSE Chemistry > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

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1
Q

Test for Hydrogen

A
  • Hold a lighted splint at the end of an open test tube
  • If a popping sound it produced, hydrogen is present
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2
Q

Test for Oxygen

A
  • Insert a glowing splint into the mouth of a flask
  • If the splint relights, oxygen is present
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3
Q

Test for Carbon Dioxide

A
  • Bubble carbon dioxide gas through limewater
  • If the limewater turns cloudy, carbon dioxide is present
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4
Q

Test for Chlorine

A
  • Hold a piece of damp blue litmus paper to the mouth of a boiling tube
  • If the paper turns red then white, chlorine is present
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5
Q

Why does the litmus paper turn red before turning white?

A
  • Chlorine dissolves in the water on the litmus paper
  • Reacts with it to form HCL
  • HCL is acid so it turns the paper red
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6
Q

Test for Cations (Flame Test)

A
  • Take a nichrome wire loop and dip it in the unknown solution
  • Hold the loop over a blue flame
  • Observe what colour the flame turns
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7
Q

What colour does Lithium (Li+) produce?

A

Crimson

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8
Q

What colour does Sodium (Na+) produce?

A

Yellow

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9
Q

What colour does Potassium (K+) produce?

A

Lilac

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10
Q

What colour does Calcium (Ca2+) produce?

A

Orange-Red

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11
Q

What colour does copper (Cu2+) produce?

A

Green

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12
Q

Test for Cations (Metal Hydroxide Test)

A
  • Add sodium hydroxide to the metal ion
  • If a coloured precipitate forms it could be 1 one of 3 cations
  • If a white precipitate forms, add excess sodium hydroxide
  • If it dissolves, Al3+ is present, if not its Mg2+ or Ca2+
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13
Q

Metal Hydroxide Precipitate Colours

A
  • Fe3+ - Brown
  • Fe2+ - Green then turns brown
  • Cu2+ - Light blue
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14
Q

Test for Carbonates

A
  • Add dilute HCL to carbonates
  • Run any gas produced in limewater through a tube
  • If carbonates are present then the limewater will turn cloudy
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15
Q

Test for Sulfates

A
  • Add barium chloride to dilute HCL
  • If a white precipitate forms sulfate is present
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16
Q

Test for Halides

A
  • Add silver nitrate to dilute nitric acid
  • If a coloured precipitate forms, a halide is present
17
Q

Halide Precipitate Colours

A
  • Iodide (I-) - Yellow
  • Bromide (Br-) - Cream
    Chloride (Cl-) - White
18
Q

What is a pure substance

A
  • All the particles are the same
  • Contains only one element/compound
  • Has a fixed melting and boiling point
19
Q

What is the difference between the term pure in advertising and a pure substance?

A
  • Pure in advertising means the product has nothing added to it and its in its natural state
  • A pure substance is made up of only one element or compound
20
Q

What is a formulation?

A

A mixture of different components each with different jobs that work together to give the formulation specific properties

21
Q

What is an emulsion?

A

A mixture of 2 things which won’t usually mix together and a special chemical called an emulsifier that makes them stick together, e.g. mayonnaise

22
Q

How can you tell when a substance isn’t pure?

A

When it’s melting and boiling points are a range instead of a specific value

23
Q

Physical Test

A

When you test the physical properties of a substance

24
Q

What do impurities do to the melting and boiling points of substances?

A
  • Decrease melting points
  • Increase boiling points
25
Q

Paper Chromatography

A

Used to separate mixtures of soluble substances

26
Q

Paper Chromatography Method

A
  • Draw a base line in PENCIL at the bottom of a sheet of filter paper
  • Draw a dot of the ink sample on the base line
  • Fill a beaker with a shallow amount of solvent (usually water or ethanol) making sure the ink and the base line don’t come into contact with it
  • Place a lid on the beaker so the solvent doesn’t evaporate
  • As the solvent seeps up the paper the present dyes dissolve in it and move up the paper
27
Q

Chromatogram

A

The result of separating mixtures by chromatography

28
Q

Mobile Phase

A
  • A substance molecules can move in
  • Is always a liquid or a gas
  • In paper chromatography it’s the solvent
29
Q

Stationary Phase

A
  • A substance molecules can’t move in
  • Is a solid but sometimes a thick liquid
  • in paper chromatography it’s the paper
30
Q

Where do soluble chemical spend more time?

A

The mobile phase (they move faster)

31
Q

Where do insoluble chemical spend more time?

A

The stationary phase (they move slower)

32
Q

RF Value

A

Distance travelled by substance/Distance travelled by solvent

33
Q

What does the chromatogram of a pure substance look like?

A
  • Doesn’t separate as it only contains one substance
  • Leaves a single dot on the filter paper
  • Different papers and solvents produce different RF values
34
Q

Flame Emission Spectroscopy

A
  • When metal ions are heated they emit light
  • The wavelength of light emitted (and the colour emitted as a result) is specific for certain metal ions
35
Q

Advantages of Flame Emission Spectroscopy

A
  • If a sample contains multiple metal ions, the spectrum shows the wavelength of all of them
  • Thickness of the lines show the concentration of the ion
  • More accurate
  • More sensitive
  • Faster than regular flame test
36
Q

Manual Tests vs Instrumental Methods

A
  • Manual - Basic but cheaper
  • Instrumental - Expensive but more accurate results

GCSE Chemistry (7 decks)

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