Tests for Water and Purity
IGCSE Edexcel Chemistry
2.49-2.50 Tests for water and purity
Key Concept:
Anhydrous copper(II) sulfate and cobalt chloride paper detect water. Pure water has a sharp boiling point.
Section A: Tests for Water
1. Describe the test for water using anhydrous copper(II) sulfate.
[2]
2. Describe the test for water using cobalt chloride paper.
[2]
Section B: Test for Purity
3. How can you show that a sample of water is pure using a physical test?
[2]
4. A sample boils over a range of temperatures. What does this suggest?
[1]
Total marks: 7
Mark Scheme
1.
White anhydrous CuSO4 turns blue in presence of water [2]
2.
Blue cobalt chloride paper turns pink when wet [2]
3.
Measure boiling point; pure water boils at 100 C (or melting point 0 C) [2]
4.
The sample is impure/a mixture [1]