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Eleanor Rowe Chemistry GCSE > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

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1
Q

What are the main features of a pure substance

A

It only contains one element or compound

Has exact melting and boiling point

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2
Q

What does impurities do to the melting and boiling points of a pure substance

A

They lower the melting point and increase the boiling point

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3
Q

What is a formulation

A

A mixture of substances where each component decides the mixtures overall properties

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4
Q

If the substance in paper chromatography travels far, what does that mean

A

It is strongly attracted to the mobile phase

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5
Q

If the substance in paper chromatography doesn’t move far what does that mean

A

It is strongly attracted to the stationary phase

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6
Q

What is the method of paper chromatography

A

Make pencil line and add drops of substance on line
Dip bottom of paper into solvent
Solvent travels up paper and picks up substances being tested and carries them up paper
Components that travel furthest are highly soluble and are minimally attracted to chromatography paper
This produces a chromatogram

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7
Q

How do you work out the Rf value

A

Distance travelled by substance divided by distance travelled by solvent

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8
Q

What is the test for hydrogen

A

Lit splint squeaky pop

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9
Q

Why does the hydrogen pop test occur

A

Hydrogen burns rapidly in presence of oxygen

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10
Q

What is the test for oxygen

A

Glowing splint relights

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11
Q

What is the test for carbon dioxide

A

Bubble through limewater and turns cloudy

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12
Q

What is the test for chlorine gas

A

Bleaches Damp litmus paper

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13
Q

What does a lilac flame show in the flame test

A

Potassium ions present

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14
Q

What does yellow flame mean in the flame tests

A

Sodium ions are present

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15
Q

What does and orange red flame mean in the flame tests

A

Calcium ions are present

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16
Q

What does a green flame mean in the flame test

A

Copper ions present

17
Q

What does a crimson flame mean in the flame tests

A

Lithium ions present

18
Q

What is the method for flame test

A

Clean wire loop in HCl
Dip loop in sample
Hold loop in blue flame of Bunsen
Record colour

19
Q

How do you test for metal hydroxide

A

Add substance to sodium hydroxide (NaOH) and colour of precipitate shows what metal hydroxide was formed
That then shows what metal ions were in substance

20
Q

If you get a white precipitate when adding NaOH to an unknown substance what metal ions could be present

A

Calcium
Aluminium
Magnesium

21
Q

If you get a brown precipitate when adding NaOH to an unknown substance what metal ions is present

A

Iron III

22
Q

If you get a blue precipitate when adding NaOH to an unknown substance what metal ions is present

A

Copper II

23
Q

If you get a green precipitate when adding NaOH to an unknown substance what metal ions is present

A

Iron II

24
Q

How do you test for carbonates in an unknown solution

A

Carbonates react with dilute acid to form salt co2 and h2o

Use standard gas test to work out if carbonate is present as it will produce co2

25
Q

How do you test for halide ions

A

Add dilute nitric acid to remove the carbonate ions
Add silver nitrate
Halide ions present= precipitate formed

26
Q

What do the different colour precipitates mean when testing for hallides

A

White means chloride
Cream means bromide
Yellow means iodide

27
Q

How do you test for sulfates

A

Add dilute HCl to solution to remove carbonates
Add barium chloride
White precipitate = sulfate present

28
Q

What are the advantages of instrumental methods

A

More sensitive and accurate
Quicker at producing results
Able to analyse small samples

29
Q

What are the disadvantages of instrumental methods

A

Expensive
Need to have special training to operate instruments
Results are often only useful when compared to data from known substances

30
Q

How does flame emission spectroscopy work

A

Place a sample of metal solution into a flame
Light is emitted and captures by spectroscope
Can distinguish between light wavelengths to produce a line spectrum
Identified metal ions, their concentration and allows us to analyse mixtures

Eleanor Rowe Chemistry GCSE (9 decks)

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