(a)[1]
State which one of these substances supplies essential minerals for aquatic life.
(b)[1]
Explain why phosphates in polluted water are harmful to aquatic life.
(c(i))[1]
Name the negative ion that is present in the highest concentration.
(c(ii))[1]
State the name of the ion $\text{NO}_3^-$.
(c(iii))[1]
Calculate the mass of phosphate ions in 200 cm$^3$ of polluted water.
(d(i))[1]
State the purpose of sedimentation in this process.
(d(ii))[1]
State why chlorine is added to drinking water.
(e)[2]
Describe how to test the purity of water by using boiling point.
(f)[2]
Complete the symbol equation for the reaction between disulfur dichloride, $\text{S}_2\text{Cl}_2$, and water. $\text{S}_2\text{Cl}_2 + .... \text{H}_2\text{O} \rightarrow .... \text{HCl} + \text{H}_2\text{SO}_3 + \text{H}_2\text{S}$