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GCSE CHEMISTRY PAPER 2 > C8 > Flashcards

C8 Flashcards

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1
Q

What is a pure substance?

A

a single element or compound not mixed with any other substances

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2
Q

How is it possible to distinguish pure substances and mixtures?

A

Pure elements and compounds melt and boil at specific temperatures

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3
Q

What is a formulation?

A

a mixture that has been designed as a useful product. They are made by mixing components in carefully measured quantities

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4
Q

Give examples of formulations

A
  • Paints
  • cleaning agents
  • fertilisers
  • alloys
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5
Q

How do you calculate the Rf value?

A

distance moved by substance/ distance moved by solvent

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6
Q

How does the chromatography of a mixture and a pure compound differ?

A

• a mixture separates into different spots depending on the solvent
• a pure compound will produce a single spot in all solvents

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7
Q

Explain the test for hydrogen

A

(the squeaky pop test)

  • a burning splint is held at the end of a test tube
  • hydrogen present = will be a squeaky pop sound
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8
Q

Explain the test for oxygen

A

uses a glowing splint inserted into a test tube of oxygen.
This will result in the splint relighting

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9
Q

Explain the test for chlorine gas

A

Use damp litmus paper.
When the damp litmus paper is put in chlorine gas the paper is bleached white

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10
Q

Explain the test for carbon dioxide

A

test for carbon dioxide involves aqueous calcium hydroxide (limewater).
When carbon dioxide is bubbled through the limewater it becomes cloudy

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11
Q

What can be used to identify some metal cations? e.g. Lithium, sodium, potassium, calcium and copper

A

Flame tests

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12
Q

What colour flame do lithium compounds result in?

A

a crimson flame

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13
Q

Which metal compound results in a lilac flame?

A

potassium

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14
Q

What colour flame do copper compounds result in?

A

a green flame

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15
Q

Which metal compound results in a yellow flame?

A

sodium

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16
Q

What colour flame do calcium compounds result it?

A

a orange-red flame

17
Q

What happens if a sample containing a mixture of ions is used?

A

Some flame colours may be masked

18
Q

What solution can be used to identify some cations?

A

Sodium hydroxide

19
Q

What is the formula for sodium hydroxide?

A

NaOH

20
Q

What hydroxide forms a white precipitate (a heavy white amorphous powder) at first but then dissolves in excess sodium hydroxide to form a colourless solution?

A

Aluminium

21
Q

What colour precipitate does a calcium solution form when NaOH is added?

A

white

22
Q

What colour precipitate does a copper solution form when NaOH is added?

A

blue

23
Q

What colour precipitate does a iron(ii) solution form when NaOH is added?

A

green

24
Q

What colour precipitate does a iron(iii) solution form when NaOH is added?

A

brown

25
Q

What colour precipitate does a magnesium solution form when NaOH is added?

A

white

26
Q

Write an ionic equation for precipitate formation for a metal ion of your choice

A

Ca2+(aq) + 2OH-(aq) → Ca(OH)2 (s)

Instructions:
metal ion + balanced hydroxide ion

product- metal followed by (OH) with the same number used in the reactants

27
Q

What can help detect carbonates? Explain the process

A

Dilute acids react with carbonates to form carbon dioxide (gas)

The carbon dioxide can be identified using limewater (calcium hydroxide)

28
Q

How can we identify sulfates?

A

adding a few drops of dilute hydrochloric acid (to get rid of carbonate ions) and then drops of barium chloride

  • sulfate ions in a solution will produce a white precipitate
29
Q

How do we identify halides?

A

Add a few drops of dilute nitric acid and then silver nitrate

A coloured precipitate will be formed depending on the halide

30
Q

What colour precipitate is formed when chloride is identified?

A

white

31
Q

What colour precipitate is formed when bromide is identified?

A

cream

32
Q

What colour precipitate is formed when iodide is identified?

A

yellow

33
Q

How else can elements be identified and what are the benefits?

A

using instrumental methods - (accurate, sensitive and rapid)

34
Q

What is flame emission spectroscopy?

A

An example of an instrumental method used to analyse metal ions in solutions

35
Q

Explain the process of flame emission spectroscopy

A
  • The sample is placed in a flame
  • As the ions heat up they move to higher energy levels and once the electrons drop back to their original energy level, they release energy as light
  • The light passes through a spectroscope and the output is a line spectrum
  • The line spectrum can be analysed to identify the metal ions in the solution and measure their concentrations

GCSE CHEMISTRY PAPER 2 (5 decks)

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