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Chemistry > Chemical analysis > Flashcards

Chemical analysis Flashcards

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1
Q

What is a pure substance?

A

A substance that only contains one element or compound

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2
Q

How can you identify a pure substance?

A

By its melting/boiling point

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3
Q

How can you tell if a substance is impure?

A

If its melting/boiling point is over a range of temperatures

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4
Q

What is chromatography used for?

A

The separation of mixtures to identify their components

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5
Q

What is the stationary phase in chromatography?

A

The paper

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6
Q

What is the mobile phase in chromatography?

A

The water or solvent

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7
Q

How do you calculate the Rf value in chromatography?

A

Distance moved by substance / distance moved by solvent

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8
Q

How do you test for hydrogen?

A

A burning splint is held at the open end of a test tube of the gas, if hydrogen is present it will make a squeaky pop sound

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9
Q

How do you test for oxygen?

A

A glowing splint is inserted into a test tube of the gas, the splint will relight if oxygen is present

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10
Q

How do you test for carbon dioxide?

A

Bubbling the gas through limewater (calcium hydroxide), the limewater will turn from clear to cloudy if carbon dioxide is present

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11
Q

How do you test for chlorine?

A

Damp litmus paper is put into the gas, it will bleach and turn white if chlorine is present

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12
Q

What are the two ways you can test for metal ions?

A

Flame tests and drops of sodium hydroxide solution

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13
Q

What colour does each metal burn:
Lithium
Sodium
Potassium
Calcium
Copper

A

Crimson
Yellow
Lilac
Orange-red
Green

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14
Q

Why might a flame test not work?

A

If the substance is impure then some colours can be masked by other brighter colours

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15
Q

What is the method for a flame test?

A

1) Dip the end of the wire in concentrated hydrochloric acid and heat it in a bunsen flame to clean it
2) Put the wire into the solid/compound
3) Hold the wire in the flame to see what colour is produced

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16
Q

When a few drops of sodium hydroxide are added, which metals produce a white precipitate?

A

Aluminium, calcium and magnesium

17
Q

When a few drops of sodium hydroxide are added, what colour precipitate does iron (II) produce?

A

A green precipitate

18
Q

When a few drops of sodium hydroxide are added, what colour precipitate does iron (III) produce?

A

A brown precipitate

19
Q

When a few drops of sodium hydroxide are added, what colour precipitate does copper produce?

A

A blue precipitate

20
Q

What metal produces a precipitate that then dissolves if sodium hydroxide is added in excess?

A

Aluminium

21
Q

How would you produce ammonia?

A

By adding sodium hydroxide and warming the solution gently; the ammonium ions should produce ammonia

22
Q

How would you test for ammonia / tell if it’s present?

A

It has a very strong smell however is colourless
It would also turn damp litmus paper blue

23
Q

How would you test for a carbonate?

A

Any carbonate will produce CO2 when a dilute acid is added and then you would use the limewater test

24
Q

What is the word equation for the limewater test?

A

Calcium hydroxide + carbon dioxide → calcium carbonate + water

25
Q

Why does the limewater turn from clear to cloudy when CO2 is present?

A

Because calcium carbonate is produced which is a solid, turning it cloudy

26
Q

How do you test for a halide ion?

A

You add silver nitrate solution (with dilute nitric acid) to a sample of the halide

27
Q

What precipitate is formed when silver nitrate solution is added to chlorine?

A

A white precipitate of silver chloride

28
Q

What precipitate is formed when silver nitrate solution is added to bromine?

A

A cream precipitate of silver bromide

29
Q

What precipitate is formed when silver nitrate solution is added to iodine?

A

A yellow precipitate of silver iodide

30
Q

How do you test for sulphates?

A

You add hydrochloric acid and barium chloride solution, a white precipitate of barium sulphate will form if the sulphate is present

31
Q

What are some examples of instrumental analysis?

A

Mass spectrometry
Flame emission spectroscopy
Gas chromatography

32
Q

What are the pros and cons of instrumental analysis?

A

Pros-
Uses smaller samples
Fast
Accurate
Gives a lot of information

Cons-
Machines / instruments can be expensive

33
Q

What are the pros and cons of chemical analysis?

A

Pros-
Often simple to do

Cons-
It uses up the sample

34
Q

What is flame emission spectroscopy used for and how is it better than a flame test?

A

To identify different ions in mixtures; this makes it more useful than flame tests which only work for substances that contain a single metal ion

35
Q

How does flame emission spectroscopy work?

A

By measuring the specific wavelength of the light emitted by each ion

36
Q

What is a formulation?

A

A mixture of different substances that forms a useful product

37
Q

What is each part of a formulation called?

A

A component

Chemistry (9 decks)

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