C8 Chemical Analysis

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What is a pure substance?
A single element or compound not mixed with any other substance
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How could you test if a substance was pure?
Melting/Boiling point
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What is special about the melting/boiling point of a pure substance?
They melt/boil at specific temperatures
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How can you determine if a substance is pure or mixture?
Compare melting/boiling point data to databases to distinguish pure substances from mixtures.
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What is a formulation?
A mixture that has been designed as a useful product
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How are formulations made?
Mixing the components in carefully measured quantities to ensure that the product has the required prperties.
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Give examples of formulations.
Fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods.
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What is chromatography?
A separation technique used to separate mixtures and give information to identify substnces.
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What does chromatography involve?
Stationary phase and mobile phase
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What does separation depend on?
The distribution of substances between the phases.
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What is the stationary phase in chromatography?
Chromatography paper
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What is the mobile phase in chromatography?
Solvent.
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Why may an ink not move during chromatography?
Not soluble in that solvent
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What is the equation for Rf value?
Rf = distance moved by substance/distance moved by solvent
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How can Rf values be used to identify compounds?
Different compounds have different Rf values in different solvents, which can be used to identify compounds using data from databases.
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What will a mixture show during chromatography?
Different number of spots depending on the solvent.
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What will a pure compound show during chromatography?
A single spot in all solvents.
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What is the test for hydrogen?
Hold a lit splint near the end of a test tube filled with gas - squeaky pop will be heard as hydrogen rapidly burns
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What is the test for oxygen?
Glowing splint inserted into test tube of gas - splint will relight in oxygen.
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What is the test for carbon dioxide?
Gas bubbled through lime water (aqueous calcium hydroxide). Carbon dioxide turns lime water cloudy/milky.
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What is the test for chlorine gas?
Using damp litmus paper, hold the paper at the test tube with the gas. If paper bleaches and turns white, chlorine gas is present.
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How can flame tests be used to identify ions?
Flame will burn different colour depending on the metal ion (cation)
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What colour will lithium burn?
Crimson flame
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What colour will sodium burn?
Yellow flame
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What colour will potassium burn?
Lilac flame
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What colour will calcium burn?
Orange-red flame
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What colour will copper burn?
Green flame
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What would happen if a sample contained a mixture of ions?
Flame colour would be masked or multiple colours.
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What is formed with sodium hydroxide and aluminium, calcium and magnesium?
White precipitates will form.
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What will happen to aluminium hydroxide precipitate in sodium hydroxide solution?
Dissolves in excess sodium hydroxide solution.
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What will form between sodium hydroxide and copper (II) ions?
Blue precipitate
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What will form between sodium hydroxide and iron (II) ions?
Green precipitate
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What will form between sodium hydroxide and iron (III) ions?
Brown precipitate
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What will form when a carbonate reacts with dilute acids?
Carbon dioxide gas
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What will form when silver nitrate is reacted with chloride ion?
White precipitate
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What will form when silver nitrate is reacted with bromide ion?
cream precipitate
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What will form when silver nitrate is reacted with iodide ion?
yellow precipitate
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What will sulfate ions form when reacted with barium chloride and dilute hydrochloric acid
white precipitate
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How can elements and compounds be detected and identified?
Using instrumental methods.
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State some advantages to instrumental methods.
Accurate, sensitive and rapid.
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What is flame emission spectroscopy?
Example of instrumental method used to analyse metal ions in solutions.
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How does flame spectroscopy work?
Sample is put into a flame and the light given out is passed through a spectroscope.
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How can this be used to identify ions?
The output, a line spectrum, can be analysed to identify the metal ins in the solution and measure concentration.
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Other cards in this set

Card 2

Front

How could you test if a substance was pure?

Back

Melting/Boiling point

Card 3

Front

What is special about the melting/boiling point of a pure substance?

Back

Preview of the front of card 3

Card 4

Front

How can you determine if a substance is pure or mixture?

Back

Preview of the front of card 4

Card 5

Front

What is a formulation?

Back

Preview of the front of card 5
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