Chemistry Chemical Analysis March 2019

Question 1

What is a pure substance? Examples?

Answer 1

A single element or compound that is not mixed with any other substance. E.g. Diamond, Oxygen and Glucose (it is only made of glucose molecules).

Question 2

What is a mixture?

Answer 2

More than one substance that are not chemically joined together. E.g. Orange Juice, Soap and Air.

Question 3

What is a formulation?

Answer 3

A mixture that has been designed as a useful product. E.g. Alloys, Fertilisers and Fuels.

Question 4

What is chromatography used for?

Answer 4

Chromatography is used to separate and analyse mixtures.

Question 5

How does chromatography work?

Answer 5

There are two phases in chromatography. The first phase is the mobile phase which is the solvent. The second phase is the stationary phase which is the piece of chromatography paper.
A phase is just a state.

Question 6

What is the test for oxygen?

Answer 6

Insert a glowing splint into a tube of unknown gas. If the splint relights oxygen is present.

Question 7

What is the test for hydrogen?

Answer 7

Insert a lit splint into a tube of unknown gas. If a squeaky pop sound is heard, hydrogen is present.

Question 8

What is the test for carbon dioxide?

Answer 8

The unknown gas is added to limewater. The limewater will go cloudy is carbon dioxide is present.

Question 9

What is the test for chlorine?

Answer 9

Insert damp red or blue litmus paper into a tube of unknown gas. If the litmus paper gets bleached chlorine is present. (If litmus paper is blue there will be a gradient from blue to red to white/bleached).

Question 10

What are cations and anions?

Answer 10

Cation - A positive ion.

Anion - A negative ion.

Question 11

What are the tests for positive ions/cations?

Answer 11

• Flame tests

- Tests with sodium hydroxide solution

Question 12

What are the tests for negative ions/anions?

Answer 12

• Test for carbonate ions.

- Test for sulfate ions.

Question 13

What is a precipitate?

Answer 13

A solid formed when solutions are mixed together.

Can sometimes be shortened to ppt.

Question 14

What is a flame test?

Answer 14

Some positive ions give distinct colours in flame tests.

• Lithium gives a crimson-red flame.
• Sodium gives a yellow-orange flame.
• Potassium gives a lilac flame.
• Calcium gives a red-orange flame.
• Copper gives a green flame.

Question 15

What is a test with sodium hydroxide solution?

Answer 15

When sodium hydroxide solution is added to a substance a precipitate is formed.

• Copper forms a blue precipitate.
• Iron II forms a green precipitate.
• Iron III forms a brown precipitate.
• Magnesium, Calcium and Aluminium all form a white precipitate (Aluminium precipitate dissolves).

Question 16

What is a test for carbonate ions?

Answer 16

Dilute acid added to substance where fizzing occurs, gas produced is placed into limewater and carbon dioxide test is done.

Question 17

what is a test for sulfate ions?

Answer 17

Dilute hydrochloric acid followed by barium chloride solution is added to substance, is a white precipitate is formed sulfate ions are present.