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Chemistry Paper 2 > C8: Chemical Analysis > Flashcards

C8: Chemical Analysis Flashcards

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1
Q

Define a pure substance:

A

A chemically pure substance is a single element or compound. It contains only one substance

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2
Q

Formulation [definition]:

A

A mixture that has been designed as a useful product

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3
Q

How are formulations made?

A

By mixing the components in carefully measured quantities to ensure that the product has the required properties

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4
Q

What are the types of formulations? [7]:

A
  • Fuels
  • Cleaning agents
  • Paints
  • Medine
  • alloys
  • Fertilisers
  • Food
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5
Q

Working out purity [2]:

A
  • Pure substances have exact and specific boiling and metal points
  • The closer the values of an experiment to those in a data book the greater the purity of a sample
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6
Q

Boiling point [definition]:

A

The temperature at which liquid turns into gas

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7
Q

Melting point [definition]:

A

The temperature at which a solid turns into a liquid

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8
Q

Impure substance [definition]:

A

Made up of more than one substance

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9
Q

More impurities in a sample will…[3]:

A
  • Increase the range of temperatures at which a sample will melt or boil
  • Decrease the melting point
  • Increase the boiling point
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10
Q

The components in formulations [2]:

A
  • In a formulation, each component helps to decide what the mixture’s overall properties are.
  • To make sure that a formulation does what it is supposed to, each chemical component must be present in a precisely measured quantity.
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11
Q

Distilled vs still water [2]:

A
  • Distilled water is chemically pure as it has no mineral ions in it
  • Still water is chemically impure
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12
Q

Chromatography [definition]:

A

Chromatography is a process that separates a mixture into its different components

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13
Q

The two phases in chromatography [2]:

A
  • Substances are picked up and carried by a mobile phase (liquid or gas).
  • The mobile phase then moves through a stationary phase (solid or viscous liquid).
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14
Q

Separation of substances in chromatography [2]:

A
  • A substance moves far if it’s more attracted to the mobile phase
  • A substance doesn’t move far if it’s more attracted to the stationary phase
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15
Q

Chromatography equation:

A

. Distance moved by the substance
R𝒻 = ——————————————————-
Distance moved by the solvent

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16
Q

How many chromatography spots are produced by pure samples, and why? [2]:

A
  • The definition of a chemically pure substance is that it consists of only a single element or compound.
  • This means that pure samples will only ever produce 1 chromatography spot regardless of solvent identity.
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17
Q

Which substance will travel more quickly in a chromatogram?

A

The substance which has a greater attraction for the mobile phase will travel more quickly

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18
Q

What type of technique is chromatography?

A

A separation technique

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19
Q

What is a chromatogram?

A

Where the results of chromatography are displayed

20
Q

In chromatography, the number of spots produced by a mixture can vary depending on…

A

which solvent is used

21
Q

Testing for hydrogen [3]:

A
  • The test for hydrogen uses a burning splint held at the open end of a test tube with gas
  • If the gas is hydrogen, a “squeaky pop” sound will be produced
  • This noise is generated because hydrogen burns rapidly in the presence of oxygen to give H₂O
22
Q

Testing for Oxygen [2]:

A
  • Insert a glowing splint into a test tube that contains a gas
  • If the gas is oxygen, the splint will relight
23
Q

Testing for Carbon dioxide [2]:

A
  • Take an aqueous solution of limewater (calcium hydroxide) and bubble through the gas
  • If the gas is carbon dioxide, the limewater solution will turn from clear to cloudy
24
Q

Testing for Chlorine [2]:

A
  • Insert damp litmus paper into a test tube that contains a gas
  • If the gas is chlorine, the litmus paper will bleach and change colour from red to white
25
Q

Which gas is being tested for if you insert a glowing splint into a test tube?

A

Oxygen

26
Q

What colour will damp litmus paper turn if it comes into contact with chlorine?

A

White

27
Q

What happens if carbon dioxide is bubbled through limewater?

A

If carbon dioxide is bubbled through limewater, the solution will turn from colourless to cloudy

28
Q

What are flame ions used to identify?

A

Metal ions (cations)

29
Q

Cu²⁺(copper) flame test:

A

Green flame.

30
Q

Ca²⁺(calcium) flame test:

A

Orange-red flame

31
Q

Na⁺(Sodium) flame test:

A

Yellow flame

32
Q

K⁺(potassium) flame test:

A

Lilac flame

33
Q

Li⁺(Lithium) flame test:

A

Crimson flame

34
Q

Flame test steps [2]:

A
  • Wet the tip of a glass rod and dip it in a salt

- Place the tip of the glass rod in the flame

35
Q

Equipment for flame tests [3]:

A
  • Glass rod/ nichrome wire loop
  • At least 4 different metal salts
  • Bunsen burner
36
Q

Why is it problematic for interpreting the results of a flame test if a sample is made up of multiple ions?

A

If the sample consists of a mixture of metal ions, the flame colours of some may be masked, which can lead to incorrect interpretations

37
Q

Metal hydroxides [2]:

A
  • Sodium hydroxide solutions can be used to identify some metal ions(cations)
  • Sodium hydroxide is added to a solution of the metal ion to be tested, a solid precipitate is formed and can be used to identify the metal ions
38
Q

Coloured precipitates in sodium hydroxide tests [3]:

A
  • Copper(II) [
  • Iron(II) [Fe²⁺]
  • Iron (III) [Fe³⁺]
39
Q

Which precipitate produced is reddish-brown in sodium hydroxide tests?

A

Fe³⁺

40
Q

Which precipitate is light green and slowly turns brown(looks dirty green) in sodium hydroxide tests?

A

Fe²⁺

41
Q

Which precipitate is light blue in sodium hydroxide tests?

A

Cu²⁺

42
Q

What are the white precipitates produced in sodium hydroxide tests? [3]:

A
  • Al³⁺
  • Ca²⁺
  • Mg²⁺
43
Q

How does one know that the precipitate produced is Al³⁺?

A

It dissolves in excess sodium hydroxide solution

44
Q

How do you distinguish between Mg²⁺ and Ca²⁺? [3]:

A
  • Both Mg²⁺ and Ca²⁺ are insoluble in excess sodium hydroxide
  • By doing the flame test you can find out which is which
  • When burning Ca²⁺ it produces a orange-red flame. Whereas Mg²⁺ produces a white flame
45
Q

Testing for Carbonates [3]:

A
  • CO₃²⁻ ions are characteristic of all carbonates.
  • A reaction between a carbonate and a dilute acid gives a salt, carbon dioxide and water.
  • As carbon dioxide is produced, we can use the standard carbon dioxide test to work out if an unknown substance is a carbonate.
46
Q

The products of a reaction between a carbonate and a dilute acid [3]:

A
  • A salt
  • Water
  • Carbon dioxide

Chemistry Paper 2 (5 decks)

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