EQ's

Question 1

Describe how you could test whether water is pure or not

[3 marks]

Answer 1

Heat the water until it boils

Measure and recordthe temperature at which it boils

If it boils at the specific and fixed temperature of 100 degrees Celcius then it is pure

Question 2

Name a process that could be used to obtain pure water from a sample of sea water

[1 mark]

Answer 2

Distillation

Question 3

In a chromatography practical a student drew the start line in ink and put a lot of water in the beaker so the start line was below the surface of the water.

Identify the errors that were made and the problems that these errors would cause

[4 marks]

Answer 3

1. Error= The start line was drawn in ink
   Problem= The ink will be dissolved in the solvent
2. Error= The start line with the coloured spots is below the surface of the water

Problem= The colours will dissolve in the solvent

Question 4

Describe how a student can use changes to limewater to measure how long it takes for carbon dioxide to be produced

[2 marks]

Answer 4

Record the time from when the heating started

Until the limewater turns cloudy white

Question 5

A teacher tested two tubes containing hydrogen.

In the first tube, she lighted a splint immediately after removing the bung.

For the second tube, she lighted the splint a few seconds after takeing the bung off.

Explain why the squeaky pop from test tube 2 would hve been louder than the one from test tube 1

Answer 5

the hydrogen had more time to mix with the oxygen that entered from the air

Question 6

Why is it necessary to add dilute nitric acid to a solution before adding dilute silver nitrate?

[1 mark]

Answer 6

To remove any carbonate impurites that may be present in the solution

Question 7

An unknown solution, Y, was tested with acidified silver nitrate solution.

Which acid was used to acidify the solution?

Answer 7

Nitric acid

Question 8

Students added a solution of ethanoic acid to an unknown compound, Z.

A gas was produced which turned limewater milky.

Name the anion present in the unknown compound (Z) and give a reason for your answer.

[2 marks]

Answer 8

Carbonate ion

The carbonate ions react with the acid to produce carbon dioxde

Question 9

What does (aq) mean?

[1 mark]

Answer 9

Aqueous solution