(a(i))[2]
Name two other harmful substances that may be found in polluted water and are dangerous to aquatic life.
(a(ii))[1]
State why sewage can cause disease.
(b(i))[1]
State the positive ion that has the lowest concentration.
(b(ii))[1]
State the name of the ion SO$_4^{2-}$.
(b(iii))[1]
Calculate the mass of calcium ions in $250\text{ cm}^3$ of polluted water.
(c(i))[1]
Describe how pink cobalt(II) chloride may be converted into blue cobalt(II) chloride.
(c(ii))[1]
Select the word from the list that most accurately describes pink cobalt(II) chloride. anhydrous, hydrated, liquid, reduced
(d)[2]
Complete the symbol equation for this reaction. 3Fe + [BLANK]H$_2$O → Fe$_3$O$_4$ + 4[BLANK]