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Chemistry AQA Triple > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

Paper 2 - C8

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1
Q

Are pure substances mixed with other substances?

A

No they aren’t

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2
Q

What type of of melting and boiling point do pure substances have?

A

Specific fixed boiling and melting points

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3
Q

What type of of melting and boiling point do impure substances have?

A

They melt and boil over a range of temperatures

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4
Q

What is a formulation?

A

A complex mixture that has been designed as a useful product.

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5
Q

What are some examples of formulations?

A

-Fuels
-Cleaning products
-Paints
-Medicines
-Alloys
-Fertilisers
-Food

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6
Q

Why are the quantity of each component carefully measured in a formulation?

A

It’s so the product has the right properties we need

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7
Q

What does paper chromatography allow us to separate?

A

Separate substances based on their different solubilities.

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8
Q

Why is the paper called the stationary phase?

A

Because it does not move

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9
Q

Why is the solvent called the mobile phase?

A

Because it does move

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10
Q

What will a pure compound produce in paper chromatography?

A

It will produce a single spot in all solvents.

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11
Q

What will compounds in a mixture produce in paper chromatography?

A

They may separate into different spots depending on the solvent.

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12
Q

Why do we draw our starting line in pencil?

A

As if we drew it in pen the ink from the pen would move up the paper with the solvent.

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13
Q

How do we calculate the Rf value of a substance?

A

Distance moved by substance
——————————————— = Rf
Distance moved by solvent

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14
Q

Why may we need to repeat the chromatography experiment when finding the Rf value of an unknown chemical?

A

-Several different substances could have the same Rf value. Which means we may have to repeat the experiment using a different solvent.
-If the substance has never been analysed before, then there will not be an Rf value on the database.

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15
Q

How do we test for Hydrogen gas?

A

-First get a test tube which may contain hydrogen.
-Remove the bung and insert a burning splint.
-If Hydrogen gas is present it will burn rapidly and produce a pop sound.

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16
Q

How do we test for Oxygen gas?

A

-First get a test tube which may contain oxygen.
-Get a glowing splint and place it into a the test tube of oxygen.
-If oxygen is present the splint relights (bursts into flames).

17
Q

How do we test for Carbon dioxide?

A

-First get a test tube which may contain carbon dioxide and get one with limewater.
-Draw some of the gas into a plastic pipette.
-Bubble the gas through the limewater and repeat this several times.
-If carbon dioxide is present the limewater will turn cloudy.

18
Q

How do we test for Chlorine?

A

-First get a test tube which may contain chlorine.
-Insert a damp litmus paper into the mouth of the test tube.
-If chlorine is present it will bleach the litmus paper and it will turn white.

19
Q

(Triple only) What colour flame does Lithium produce?

A

A Crimson flame

20
Q

(Triple only) What colour flame does Sodium produce?

A

A Yellow flame

21
Q

(Triple only) What colour flame does Potassium produce?

A

A Lilac flame

22
Q

(Triple only) What colour flame does Calcium produce?

A

An Orange-red flame

23
Q

(Triple only) What colour flame does Copper produce?

A

A Green flame

24
Q

(Triple only) What are the problems with flame tests?

A

-The colour of a flame test can be difficult to distinguish. That is especially true if there is only a low concentration of the metal compound.
-Sometimes a sample contains a mixture of metal ions with can mask the colour of the flame.

25
Q

(Triple only) What other process can we use instead of flame tests?

A

Flame emission spectroscopy

26
Q

(Triple only) What happens in Flame emission spectroscopy?

A

-A sample of the metal ion in solution is placed into a flame.
-The light given out is then passed into a machine called a spectroscope.
-The spectroscope converts the light into a line spectrum.
-And the positions of the lines in the spectrum are specific for a given metal ion so we can use this to identify the metal ion in the sample.

27
Q

(Triple only) What is Flame emission spectroscopy an example of?

A

An instrumental method

28
Q

(Triple only) What are the advantages of Flame emission spectrocsopy?

A

-Instrumental methods are rapid. Meaning we can use flame emission spectroscopy to analyse sample more rapidly than we could using flame tests.
-Instrumental methods are sensitive. Flame emission spectroscopy will work even on a tiny sample of metal compound.
-Instrumental methods are accurate. Flame emission spectroscopy is more likely to identify a metal ion correctly than using a flame test.

29
Q

(Triple only) What colour precipitate does copper (II) ions produce when reaction with sodium hydroxide?

A

Blue precipitate of copper (II) hydroxide

30
Q

(Triple only) What colour precipitate does iron (II) ions produce when reaction with sodium hydroxide?

A

Green precipitate of iron (II) hydroxide

31
Q

(Triple only) What colour precipitate does iron (III) ions produce when reaction with sodium hydroxide?

A

Brown precipitate of iron (III) hydroxide

32
Q

(Triple only) How do we test for a carbonate ion?

A

1) Add dilute acid to our sample.
2) The acid will react with the carbonate to make carbon dioxide gas. We will see effervescence (fizzing).
3) Bubble the gas through lime-water. If the lime-water goes cloudy, then this proves that we have carbon dioxide. Which means we started with the carbonate ion.

33
Q

(Triple only) How do we test for halide ions?

A

1) Add dilute nitric acid to our sample.
2) Add dilute silver nitrate solution.
3) Halide ions produce a precipitate of the silver halide. Each halide makes a different coloured precipitate.

34
Q

(Triple only) What colour precipitate do Chloride ions produce?

A

White precipitate of silver chloride

35
Q

(Triple only) What colour precipitate do Bromide ions produce?

A

Cream precipitate of silver bromide

36
Q

(Triple only) What colour precipitate do Iodide ions produce?

A

Yellow precipitate of silver iodide

37
Q

(Triple only) How do we test for sulfate ions?

A

1) Add dilute hydrochloric acid to our sample.
2) Add barium chloride solution.
3) If sulfate ions are present, we will see a white precipitate.

Chemistry AQA Triple (17 decks)

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