Which statement about water is correct?
It turns anhydrous copper(II) sulfate from pink to blue.
It turns anhydrous copper(II) sulfate from white to blue.
It turns cobalt(II) chloride paper from blue to white.
It turns cobalt(II) chloride paper from pink to blue.
B
Which statement identifies a sample of water as pure?
It melts at room temperature.
It turns anhydrous copper(II) sulfate blue.
It turns hydrated cobalt(II) chloride from blue to pink.
It boils at 100∘C.
D
Which pollutant leads to the deoxygenation of water in ponds and lakes?
fertilisers containing nitrates and phosphates
toxic metal compounds
combustion products of fossil fuels
acid rain
A
Which statements about the treatment of domestic water supplies are correct?
1 Filtration is used to remove insoluble substances from the water.
2 Sedimentation is used to remove soluble substances from the water.
3 Carbon is used to remove tastes and odours from the water.
4 Chlorine is used to lower the pH of the water.
1 and 3
1 and 4
2 and 3
2 and 4
A