AQA Chemistry Topic 8: Chemical Analysis

Chemistry aqa 2025 higher

What is a formulation?

A complex mixture designed to be a useful product

Name 3 formulations

Alloys, fertilisers, food

What is the hydrogen test?

Squeaky pop test

How do you do the squeaky pop test?

1. test tube with bung covered

2. light match

3. remove bung and place match on top

4. a loud pop means it has hydrogen

How do we do the test for oxygen?

1. remove bung from test tube

2. place a glowing splint in the tube

3. if it relights it has oxygen

What is the test for carbon dioxide?

Cloudy water

How do we do the cloudy water test?

1. Use a plastic pipette to draw some CO2 out

2. Pour out the CO2 in the limewater

3. If it turns cloudy it's CO2

What is limewater?

Aqueous solution of calcium hydroxide

What is the chlorine test?

1. Place damp litmus paper near the mouth of the test tube

2. Chlorine will bleach it

How do we do the flame test?

1. Place small amount of chemical on wire mounted with handle

2. Place it on the end of a blue flame on a bunsen burner

3. Colour tells you what metal ion it is

What colour is lithium?

Crimson

What metal ion produces a green flame?

Copper

What colour is Potassium

lilac

What colour is calcium

orange-red

What metal ion produces a yellow colour

Sodium

What are two problems with flame tests?

1. Colour is hard to distinguish especially with small amounts

2. There may be a mixture of different ions which may cause different colours

How does flame emission spectroscopy work?

1. Sample of metal ion in solution is placed onto a flame

2. The colour emitted is passed through a spectroscope

3. Which converts the colour into a line spectrum

4. The colour is specific to a metal ion so you can use it to identify a metal ion

What does having a more intense line on a line spectrum mean?

higher solution

What is an instrumental method?

A method carried out by a machine

What are two pros of instrumental methods?

1. They are rapid

2. They are sensitive so work even on small amount

3. Accurate

What 3 ions form white precipitates when added to sodium hydroxide

1. Magnesium

2. Aluminium

3. Calcium

How do we identify aluminium ions?

Add excess sodium hydroxide and it should redissolve

How do we identify Calcium ions?

Flame test, calcium turns orange-red

Of all the 3 hydroxide tests what is the one that uses 3 and not 2 for its balanced equation?

Aluminium

What colour precipitate does copper II form

Blue

What colour precipitate does Iron II form

green

What colour precipitate does Iron III form

Brown

What are the 2 products of a metal hydroxide test?

Sodium Nitrate and Metal Hydroxide

How do we test for carbonate ions?

1. add dilute acid to sample

2. acid and carbonate react to form CO2 and fizzing

3. Bubble it through limewater

4. If cloudy then it is carbonate ion

What is effervescence?

Fizzing

How do we test for halide ions?

1. Add dilute nitric acid to sample

2. Add silver nitrate to solution

3. Different halides form different precipitates

What precipitate does iodine form?

yellow

What halide forms a white precipitate?

Chloride

What precipitate does bromide form?

Cream

What is the test for sulfate ions?

1. Add dilute hydrochloric acid to sample

2. Add Barium Chloride to solution

3. Sulfate ions form a white precipitate