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GCSE Triple Chemistry > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

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1
Q

What is a pure substance?

A

A substance with only one element/compound present

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2
Q

Name a characteristic of pure substances

A

They have a specific melting/boiling point

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3
Q

How can you test is a substance is pure or not?

A

Boil it. If it has one set boiling point it is pure.

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4
Q

What do impurities do to the melting/boiling point of a substance?

A

Raise/Lower it. Impure substances will not melt/boil at a set temperature.

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5
Q

What is a formulation?

A

A mixture that has been designed as a useful product.

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6
Q

What is the equation for percentage composition?

A

(amount of desired mass / total mass) x 100

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7
Q

In Paper Chromatography, which is the stationary phase?

A

The paper

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8
Q

In Paper Chromatography which is the mobile phase?

A

The water

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9
Q

What is phase distribution?

A

The attraction of the substance to the paper in relation to its attraction to the solvent.

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10
Q

What happens to substances with a stronger attraction to the solvent?

A

They will travel faster and further up the paper

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11
Q

What happens to substances with a stronger attraction to the paper?

A

They will move slowly and not very far up

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12
Q

What does the separation of the solute depend on?

A

The solubility and its attraction to the stationary phase.

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13
Q

What is the Rf value?

A

The ratio of the distance moved by the substance to the distance moved by the solvent

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14
Q

How do you calculate the Rf value?

A

Distance moved by substance / Distance moved by solvent

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15
Q

Describe how you would carry out a test for Hydrogen

A
  1. Put 5cm depth of HCl into a test tube
  2. Add a piece of Mg ribbon and seal the test tube with a bung
  3. Wait for the reaction to happen, you will see fizzing
  4. Light a splint, remove the bung, then hold the lit splint to the mouth of the test tube.
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16
Q

What is a positive result for a Hydrogen Test?

A

There will be a squeaky pop if hydrogen is present

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17
Q

Describe how to carry out a test for Oxygen:

A
  1. Add 5cm depth of Hydrogen Peroxide into a test tube
  2. Stand the tube in a rack in the sink
  3. Add a small amount of manganese dioxide
  4. Light a splint and tap it gently so it is only glowing
  5. Hold the splint to the mouth of the test tube and observe the results
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18
Q

What is a positive result of an oxygen test?

A

The glowing splint should reignite

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19
Q

Describe how to carry out a test for Carbon Dioxide:

A
  1. Half fill a test tube with limewater and place it in a test tube rack
  2. Put the end of a delivery tube in the limewater
  3. In another test tube add 5cm^3 of HCl and a spatula of Calcium carbonate
  4. Quickly put a bung in this tube and observe the limewater
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20
Q

What happens to limewater in the presence of CO2

A

It goes cloudy

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21
Q

Describe how to test for Chlorine:

A
  1. Set up an electrolysis cell with aqueous sodium chloride
  2. Apply current and wait for products to form
  3. Dip a piece of litmus paper in the solution and observe the results
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22
Q

What is a positive result for a chlorine test?

A

The solution will bleach the litmus paper

23
Q

How do you conduct a flame test?

A
  1. Dip a piece of platinum wire into the aqueous metal solution
  2. Hold the piece of wire over a lit bunsen burner and observe the colour of the flame
24
Q

Why should you use platinum wire rather than a splint for a flame test?

A

It is unreactive so won’t affect the colour of the flame, whereas a wooden splint will.

25
Q

What colour does Lithium burn?

A

Crimson red

26
Q

What colour does Sodium burn?

A

Yellowy Orange

27
Q

What colour does Potassium burn?

A

Lilac

28
Q

What colour does Calcium burn?

A

Orangey-red

29
Q

What colour does Copper burn?

A

Green

30
Q

What is the issue with wet flame tests?

A

It can be hard to judge the difference between similar colours with the eye eg. Calcium and Sodium have similar coloured flames

31
Q

How does a Flame Emission Spectrocsopy work?

A

It measures the wavelength of the flames’ light

32
Q

What are the advantages of FES over wet flame tests?

A
  • They’re more accurate
  • They leave no room for human error
  • They can measure the concentration of a metal using light intensity
33
Q

What compound do you use in Cation tests?

A

Sodium Hydroxide

34
Q

What colour precipitate does Aluminium produce?

A

White

35
Q

What happens to the Aluminium precipitate in excess sodium hydroxide?

A

It redissolves

36
Q

What colour precipitate does Calcium produce?

A

White

37
Q

What colour precipitate does Magnesium produce in the presence of NaOH?

A

White

38
Q

What colour precipitate does Copper produce?

A

Blue

39
Q

What colour precipitate does Iron (II) produce?

A

Green

40
Q

What colour precipitate does Iron (III) produce?

A

Brown

41
Q

How can we differentiate between Aluminium, Calcium and Magnesium precipitates?

A

Add excess NaOH to all the test tubes; the one which goes clear contains aluminium. To differentiate between the other two, conduct flame tests, Calcium will burn Orangey red.

42
Q

Describe how to test for Carbonate Ions

A
  1. Add a dilute acid to the sample
  2. The acid will react with the carbonate and we will observe bubbles
  3. Bubble the gas through limewater and if there was carbonate present in the sample the limewater should go cloudy
43
Q

Acid and a metal carbonate = ?

A

Acid + Metal Carbonate –> Salt + Water + Carbon Dioxide

44
Q

Describe the test for sulphates

A
  1. Add dilute HCl to the sample
  2. Add barium chloride solution
  3. If sulphate ions are present, we will see a white precipitate
45
Q

Describe the test for Halides

A
  1. Add dilute nitric acid to the sample
  2. Add dilute silver nitrate solution
  3. Each Halide will produce a precipitate of the silver halide
46
Q

What colour is the Silver Iodide precipitate?

A

Yellow

47
Q

What colour is the Silver Bromide precipitate?

A

Cream

48
Q

What colour is the Silver Chloride precipitate?

A

White

49
Q

What charge do metal ions have?

A

Positive

50
Q

What charge do non-metal ions have?

A

Negative

51
Q

Are metal ions cations or anions?

A

Cations

52
Q

Are non-metal ions cations or anions?

A

Anions

53
Q

Why does sulfur turn water cloudy?

A

It’s insoluble in water

GCSE Triple Chemistry (9 decks)

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