4.3

Question 1

4.3 Identifying unknowns (3) • To identify the positive and negative inorganic ions in five solutions, using appropriate apparatus and procedures.

Answer 1

You are given five unknown solutions. Using these chemicals only and pH indicator paper you should carry out a series of tests to allow you to identify each solution A–E

Question 2

Equipment

Answer 2

• pH indicator paper
• wash bottle containing distilled (or de-ionised water)
• measuring cylinder (25 cm3)
• beaker (100 cm3)
• glass rod
• conical flask (100 cm3)
• test-tube holder
• four test tubes
• dropping pipettes
• spatula

Question 3

Procedure

Answer 3

The identities of the solutions A–E are listed below in no particular order:
•	nitric acid, HNO3 (aq)
•	potassium iodide, KI (aq)
•	sodium carbonate, Na2CO3 (aq)
•	sodium chloride, NaCl (aq)
•	silver nitrate, AgNO3 (aq)

1. Plan and carry out a series of tests that would allow you to identify each solution A–E.
2. You should carry out the minimum number of tests required. Each test should produce a positive result for at least one of the solutions A–E.
3. Record the tests you carried out.
4. Record all the observations for your tests on solutions A–D.
5. Record your conclusions for each test.
6. Record the identity of each solution

Question 4

1. Write the equations for the reactions you have observed.

Answer 4

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Question 5

2. Write methods for the experiments you have carried out.

Answer 5

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