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GCSE Chemistry LTS > Chapter 12 Chemical Analysis > Flashcards

Chapter 12 Chemical Analysis Flashcards

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1
Q

What is an element?

A

Elements are made up of only one type of atom.

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2
Q

What is a compound?

A

Compounds are made up of 2 or more types of atoms chemically joined together.

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3
Q

What is a mixture?

A

Mixtures are made up of 2 or more substances that are not chemically joined together.

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4
Q

What is a pure substance?

A

Pure substances are made from a single element or compound.

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5
Q

What does ‘pure’ mean in everyday language?

A

In everyday language the word ‘pure’ is used differently to mean that something has not had anything added to it. This is different from the chemical meaning of pure.

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6
Q

What is an impure substance?

A

Impure substances are made of mixtures of different substances.

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7
Q

How can a pure substance be determined using melting or boiling points?

A

Pure substances have melting and boiling points that are specific.
Example: The boiling point of water is 100C.

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8
Q

How can an impure substance be determined using melting or boiling points?

A

Impure substances melt and boil over a range of temperatures.

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9
Q

What is a formulation?

A

A formulation is a mixture that has been designed as a useful product.

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10
Q

How are formulations made?

A

Formulations are made by mixing components in carefully measured quantities to ensure that the product has the required properties.

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11
Q

Give 8 examples of formulations.

A

Examples of formulations include fuels, cleaning agents, cosmetics, paints, medicines, alloys, fertilisers and foods.

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12
Q

How can pigments be separated from a mixture?

A

Paper chromatography is a separation technique used to separate mixtures of soluble substances like pigments.

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13
Q

What is a pigment?

A

A pigment is a coloured substance.

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14
Q

What are the 2 phases in chromatography?

A

In chromatography there are 2 phases called the mobile phase and stationary phase.

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15
Q

What is the mobile phase?

A

The solvent is the mobile phase. It moves through the paper carrying the different substances with it.

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16
Q

What is the stationary phase?

A

The stationary phase is the absorbent paper.

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17
Q

What do we call the paper with separated substances on it?

A

Once the substances are separated on the paper we call the paper a chromatogram.

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18
Q

Are the most soluble substances at the top of a chromatogram or at the bottom?

A

The more soluble a substance is the further it moves up the paper.

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19
Q

What is the formula for Rf value?

A

The Rf value is the distance moved by the substance divided by the distance moved by the solvent.
Rf = distance moved by substance
distance moved by solvent

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20
Q

Why is the Rf useful in identifying substances?

A

Different compounds have different Rf values in different solvents. You can use rf values of known compounds to identify unknown compounds on your chromatogram.

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21
Q

Why do we need tests to identify some gases?

A

Many gases are clear, colourless and odourless. We use specific tests to tell the difference between these gases.

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22
Q

What is the test for hydrogen gas?

A

The test for hydrogen gas is that it burns with a squeaky ‘pop’. A burning splint is used for this test.

23
Q

What is the test for oxygen gas?

A

The test for oxygen gas is that it relights a glowing splint.

24
Q

What is the test for carbon dioxide gas?

A

The test for carbon dioxide gas is that when bubbled through lime water the lime water changes from clear to cloudy.

25
Q

What is the test for chlorine gas?

A

The test for chlorine gas is that damp litmus paper (either blue or red) is bleached to white.

26
Q

What sort of test is used to identify metal ions?
(TRIPLE ONLY)

A

Flame tests can be used to identify metal ions.

27
Q

Describe how to do a flame test.
(TRIPLE ONLY)

A

To do a flame test a metal loop can be dipped in a solid compound containing the metal ion and placed in a hot Bunsen flame. The flame will change colour depending on which metal ions are in the compound.

28
Q

What colour will substances with Lithium ions burn?
(TRIPLE ONLY)

A

Lithium ions (Li+) will burn with a crimson red flame.

29
Q

What colour will substances with Sodium ions burn?
(TRIPLE ONLY)

A

Sodium ions (Na+) will burn with a yellow flame.

30
Q

What colour will substances with Potassium ions burn?
(TRIPLE ONLY)

A

Potassium ions (K+) will burn with a lilac flame.

31
Q

What colour will substances with Calcium ions burn?
(TRIPLE ONLY)

A

Calcium ions (Ca2+) will burn with an orange-red flame.

32
Q

What colour will substances with Copper(II) ions burn?
(TRIPLE ONLY)

A

Copper(II) ions (Cu2+) will burn with a green flame.

33
Q

Why is it difficult to identify mixtures of ions using a flame test?
(TRIPLE ONLY)

A

Mixtures of ions may make identification of ions difficult as some colours will be masked.

34
Q

How can you identify the metal ions in a salt solution?
(TRIPLE ONLY)

A

To identify a metal ion in a salt sodium hydroxide can be used. A metal hydroxide is produced.

35
Q

What happens when aluminium, calcium and magnesium react with sodium hydroxide solution.
(TRIPLE ONLY)

A

Aluminium, calcium and magnesium ions form a white precipitate when reacted with sodium hydroxide solution.

36
Q

Give the ionic equation for the reaction of sodium hydroxide with aluminium ions.
(TRIPLE ONLY) (HIGHER ONLY)

A

The ionic equation for the reaction with aluminium ions is:

37
Q

How will Copper(II), Iron(II) and Iron(III) ions react with sodium hydroxide?
(TRIPLE ONLY)

A

Copper(II), Iron(II) and Iron(III) ions will react with sodium hydroxide to produce coloured precipitates.

38
Q

What colour is the precipitate formed when copper(II) ions react with sodium hydroxide?
(TRIPLE ONLY)

A

Copper(II) ions form a blue precipitate.

39
Q

What colour is the precipitate formed when iron(II) ions react with sodium hydroxide?
(TRIPLE ONLY)

A

Iron(II) ions form a green precipitate.

40
Q

What colour is the precipitate formed when iron(III) ions react with sodium hydroxide?
(TRIPLE ONLY)

A

Iron(III) ions form a brown precipitate.

41
Q

What is the ionic equation for the reaction of sodium hydroxide with iron(II) ions.
(TRIPLE ONLY) (HIGHER ONLY)

A

The ionic equation for the reaction with iron(II) ions is:
Fe2+(aq) + 2OH-(aq) → Fe(OH)2(s)

42
Q

Write the word and chemical equations for the reaction of magnesium carbonate with dilute hydrochloric acid.
(TRIPLE ONLY)

A

Carbonates react with dilute acids to produce carbon dioxide.
Example:

43
Q

What is the gas produced when carbonates react with dilute acids?
(TRIPLE ONLY)

A

The gas produced in the reaction between carbonates and dilute acids can be bubbled through lime water to prove that carbon dioxide is produced.

44
Q

Write the ion equation for the reaction of a carbonate with an acid.
(TRIPLE ONLY) (HIGHER ONLY)

A

The reaction of a carbonate with an acid can be represented by just showing the ions that change in the reaction.
Example:

45
Q

What are halides? Give 3 examples.
(TRIPLE ONLY)

A

Halides are ions formed from halogens. For example iodide ions (I-), bromide ions (Br-) and chloride ions (Cl-) are all halides.

46
Q

Describe the test for halides.
(TRIPLE ONLY)

A

The test for halides involves:
1. Adding dilute nitric acid. This dissolves the ion and removes any carbonates.

  1. Add silver nitrate solution.
  2. Observe the precipitate formed.
47
Q

What is the result of the test for halides for iodide, bromide and chloride ions?
(TRIPLE ONLY)

A

The results of the test for halides are:

48
Q

Give the ionic equation for the reaction between a halide and the silver ions in the silver nitrate.
(TRIPLE ONLY) (HIGHER ONLY)

A

The ionic equation for the reaction between a halide and the silver ions in the silver nitrate is:
Ag+(aq) + X-(aq) → AgX(s)

49
Q

Give the test for sulphate ions.
(TRIPLE ONLY)

A

The test for sulphate (SO42-) ions involves:
1. Add dilute hydrochloric acid to the sample.

  1. Add barium chloride solution.
  2. Look for a white precipitate
  3. If there is a white precipitate then sulfate ions are present.
50
Q

Give the ionic equation for the reaction between barium ions and sulphate ions.
(TRIPLE ONLY) (HIGHER ONLY)

A

The ionic equation for the reaction between barium ions and sulphate ions is:
Ba2+(aq) + SO42-(aq) → BaSO4(s)

51
Q

Give 3 reasons why instrumental methods are used for the identification of elements and compounds.
(TRIPLE ONLY)

A

Elements and compounds can be detected and identified using instrumental methods. These methods are fast, accurate (close to the actual true value) and sensitive (they can detect small quantities).

52
Q

Why don’t we always just use instrumental methods for the identification of elements and compounds.
(TRIPLE ONLY)

A

Instrumental methods can be expensive and they require special training to use.

53
Q

Give an example of an instrumental method used to detect metal ions in a solution.
(TRIPLE ONLY)

A

Flame emission spectroscopy is an example of an instrumental method. It is used to detect metal ions in a solution.

54
Q

Give 2 things flame emission spectroscopy be used for.
(TRIPLE ONLY)

A

Flame emission spectroscopy results in a line spectrum that can be used to identify the metal ions present as well as the concentration of the ions.

GCSE Chemistry LTS (15 decks)

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