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Chemistry GCSE > Topic 10 - Tests for Ions > Flashcards

Topic 10 - Tests for Ions Flashcards

1
Q

What are flame tests used for

A

To identify metal ions in substances

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2
Q

How do you carry out a flame test?

A
  • light a Bunsen burner and open the air hole to give a hot blue flame
  • pick up a small sample of the test substance using a wire loop
  • Hold the sample at the top of the flame and observe the flame colour
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3
Q

What is the wire loop cleaned in?

A

Hydrochloric acid

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4
Q

What metal is the wire loop and why?

A

Platinum wire -> it has a high melting point and it is unreactive -> It also gives no colour to the flame

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5
Q

What is a cheaper wire that could be used?

A

nichrome alloy -> although it produces its own orange colour it is much cheaper

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6
Q

What are the cations that are tested?

A
  • lithium
  • potassium
  • sodium
  • calcium
  • copper
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7
Q

What colour does the flame go for the cation - lithium?

A

Red

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8
Q

What colour does the flame go for the cation - sodium?

A

Yellow

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9
Q

What colour does the flame go for the cation - potassium?

A

Lilac

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10
Q

What colour does the flame go for the cation - calcium?

A

Orange-red

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11
Q

What colour does the flame go for the cation - copper?

A

Blue-green

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12
Q

How does using scientific instruments to observe flame test improve the experiment?

A
  • sensitivity (they can detect much smaller amounts)
  • accuracy (they give values closer to the true values)
  • Speed
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13
Q

Flame photometer

A

Measure the light intensity of the flame colours produced by metal ions
-> it’s data is used to determine the concentration of a metal ion in a dilute solution

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14
Q

How does a flame photometer create accurate results of colours?

A

It separates these colours to produce a spectrum of the light emitted by each metal ion
-> different metal ions produce different emission spectra
-> a metal ion in an unknown solution could be identified by matching its spectrum to the spectrum from a known metal ion

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15
Q

precipitation reactions involving sodium hydroxide

A

they form the basis of a test to identify dissolved metal ions

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16
Q

iron(II) hydroxide precipitate colour

A

green

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17
Q

iron(III) hydroxide precipitate colour

A

brown

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18
Q

cooper hydroxide precipitate colour

A

Blue

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19
Q

calcium hydroxide precipitate colour

A

white

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20
Q

aluminium hydroxide precipitate colour

21
Q

how are ammonium ins detected

A
  • react with sodium hydroxide solution and gently warm the mixture
  • Ammonia gas is produced and can be identified by sharp smell
  • confirmatory Test is used to identify ammonia as it changes the colour of damp red litmus paper to blue
22
Q

How to identify carbonate ions?

A

Add dilate hydrochloric acid to the test substance and look for bubbling caused by the production of carbon dioxide -> the bubbles could be due to a different gas (e.g. hydrogen) so carry out a confirmatory test -> if the bubbles do contain carbon dioxide they turn lime water milky

23
Q

How to identify sulphate ions?

A

Add a teardrops die hydrochloric acid which acidifies and removes carbonate ions that might also give a precipitate in the test, then add a few drops of barium chloride solution -> if a white precipitate of barium sulphate forms the sample contains sulphate ions

24
Q

How to identify halide ions

A
  • Silver fluoride soluble in water, but the other silver halides are insoluble
  • to detect these ions in a solution add a few drops of dilute nitric acid, this acidifies the solution and remove carbonate ions that might also give a precipitate in the test
  • then add a few drops of silver nitrate solution -> different coloured silver halide precipitate forms depending on the halide ion present
25
What are the positive ions you can test for?
- metal ions and ammonium ions
26
What are the negative ions you can test for?
- carbonate ions -Sulphate ions - halide ions
27
Silver Chloride ion precipitate colour
white
28
Silver Bromide ion precipitate colour
Cream
29
Silver Iodide ion precipitate colour
Yellow
30
CORE PRACTICAL - IDENTIFYING IONS method (flame tests for metal cations, hydroxide precipitate tests for metal cations, ammonium ions, carbonate ions, sulphate ions halide ions)
Flame test for metal cations: - light a Bunsen burner and open the air hole to give a hot blue flame - Pick up a sample of a solid cell using a clean wire loop -> hold the sample in the edge of the flame - observe and record the flame colour Hydroxide precipitate test for metal cations: - Dissolve a little solid salt in a test tube using distilled water - Add a few drops of dilute sodium hydroxide solution, one drop at a time - Record the colour of any precipitate formed - If a white precipitate forms add excess dilute sodium hydroxide solution to see if it will disappear to leave a clear solution Testing for ammonium ions: - Dissolve a little solid salt in a test tube using distilled water - Add dilute sodium hydroxide solution and then warm gently - Remove from the flame, hold a piece of damp red litmus paper near the mouth of the test tube - record what happens to its colour Testing for carbonate ions: - Put a little solid salt in a test tube and had a few drops of dilute acid - Record whether any bubbling occurs - Use lime water to check that any bubbles contain carbon dioxide Testing for sulphate ions: - Dissolve a little solid salt in a test tube using distilled water - add a few drops of dilute hydrochloric acid, then a few drops of barium chloride solution - record whether a white precipitate forms Testing for halide ions: - dissolve a little solid salt in a test tube using distilled water - Add a few drops of dilute nitric acid, then a few drops of silver nitrate solution, record the colour of any precipitate formed
31
Ceramics - properties
- range of durable compounds that change very little when heated -> consist of giant structures with many strong bonds - chemically unreactive, hard and stiff but brittle - Poor electrical and thermal conductors - Have high melting points
32
How is Clay made?
Mineral Formed from weathered and decomposed rock, it is so funny it’s dug up out the ground which makes it easy to mould into different shapes so it requires to be heated at high temperatures to harden it
33
How is glass made?
By melting sand, then allowing it to cool and solidify
34
Name some clay ceramics
Brick, porcelain and China
35
How is the modern window glass made?
Using the float process -> molten glass is poured onto a bath of molten tin where it spreads out on the surface -> the flat layer of glass is drawn away and cooled in a continuous process
36
Polymer properties
- Electrical and thermal insulators - often flexible and can be easily moulded into almost any shape
37
Composite material
Mixture of two or more materials combined to produce a material within improve properties
38
Metal properties
- good conductors of heat and electricity - Have high density and a malleable - can be mixed with other elements to form alloys making them stronger
39
matrix
result of one material embedded in another (surround the reinforcement of material binding the fibres together)
40
Reinforcement
Material added to the matrix to enhance overall properties of the composite material
41
How is concrete made?
- mix cement, sand, aggregate and water together - As the concrete sets hard chemical reaction reactions happen that bond the solid compounds together - The sand and aggregate form the reinforcement of the concrete - The reinforcement is bonded together by cement
42
How is fibreglass made?
- Thin glass fibres form the reinforcement and a polymer resin forms the matrix
43
Nano particles
Really really tiny particles
44
Are Nano particles larger than atoms
Yes
45
Are nano particles smaller than cells
Yes
46
Nano particulate materials
Substances that consist of nano particles
47
What’s the surface to volume ratio like of nano particles
- very large - As a particles decrease in size the size of the surface area increases in relation to their volume so their surface area to volume ratio increases
48
What are some uses of nano particulate muscles?
- Sunscreen have been made using nano particles to not leave white marks on the skin because it’s transparent due to the particles being very small - Useful as catalysts due to very large surface area to volume ratios
49
What are the risks of nano particles?
- Nano particulate materials may post hazard to human health and the environment -> due to the small size of nano fatty it allows them to be breathed in and for them to pass through cell-surface membranes - The large sub area of volume ratios may allow them to catalyse harmful reactions or to carry substances bound to their surfaces

Chemistry GCSE (11 decks)

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