(a)[1]
From the list, select the gas required by aquatic organisms.
(b(i))[1]
Name one other harmful substance present in polluted water.
(b(ii))[1]
State why nitrates are harmful to aquatic organisms.
(c(i))[1]
Name the negative ion present in the greatest concentration.
(c(ii))[1]
State the name of the $\text{NH}_4^+$ ion.
(c(iii))[1]
Calculate the mass of calcium ions in $200\,\text{cm}^3$ of polluted water.
(d(i))[1]
State the meaning of the term hydrated.
(d(ii))[1]
Describe how hydrated copper(II) sulfate is changed into anhydrous copper(II) sulfate.
(e)[2]
Complete the symbol equation for the reaction of sodium with water. $2\text{Na} + \ldots\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \ldots$