(a(i))[1]
Identify the positive ion with the greatest concentration.
(a(ii))[1]
State the name of the $\mathrm{PO_4^{3-}}$ ion.
(a(iii))[2]
Describe a test for the presence of nitrate ions, $\mathrm{NO_3^-}$, in a water sample. Include the test and the test result.
(a(iv))[1]
Calculate the mass of sodium ions, $\mathrm{Na^+}$, in $200\,\text{cm}^3$ of the contaminated water.
(a(v))[1]
State a source of a higher concentration of nitrate ions in river water.
(b)[1]
State one method of removing the insoluble substances from the water.
(c(i))[1]
Suggest a source of the microbes in the water.
(c(ii))[1]
State how the water is treated so that the microbes do not cause harm to people.
(d)[1]
State the name of a substance that is added to remove the bad taste and odour from the water.