Which statement identifies a sample of water as pure?
A.
It melts at room temperature.
B.
It turns anhydrous copper(II) sulfate blue.
C.
It turns hydrated cobalt(II) chloride from blue to pink.
D.
It boils at \(100^{\circ} \mathrm{C}\).
Exam No：0620_s24_qp_21 Year：2024 Question No：34
Answer:
D
Knowledge points:
10.1.1. Describe chemical tests for the presence of water using anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate
10.1.2. Describe how to test for the purity of water using melting point and boiling point
10.1.3. Explain that distilled water is used in practical chemistry rather than tap water because it contains fewer chemical impurities
10.1.4.1. dissolved oxygen
10.1.4.2. metal compounds
10.1.4.3. plastics
10.1.4.4. sewage
10.1.4.5. harmful microbes
10.1.4.5. harmful microbes
10.1.4.6. nitrates from fertilisers
10.1.4.7. phosphates from fertilisers and detergents
10.1.5.1. dissolved oxygen for aquatic life
10.1.5.2. some metal compounds provide essential minerals for life
10.1.6.1. some metal compounds are toxic
10.1.6.2. some plastics harm aquatic life
10.1.6.3. sewage contains harmful microbes which cause disease
10.1.6.4. nitrates and phosphates lead to deoxygenation of water and damage to aquatic life Details of the eutrophication process are not required
10.1.7.1. sedimentation and filtration to remove solids
10.1.7.2. use of carbon to remove tastes and odours
10.1.7.3. chlorination to kill microbes
Solution:
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