(a)[1]
Balance the equation for the first stage in the manufacture of nitric acid from ammonia: $\text{NH}_3 + \text{O}_2 \rightarrow \text{NO} + \text{H}_2\text{O}$.
(b(i))[1]
Name the alkali that reacts with dilute nitric acid in order to produce potassium nitrate.
(b(ii))[2]
Describe the method used to make colourless aqueous potassium nitrate from the alkali and dilute nitric acid.
(b(iii))[2]
Calculate the percentage by mass of nitrogen present in potassium nitrate.
(c(i))[1]
Name one additional pollutant that can be found in river water.
(c(ii))[3]
State three processes used to purify river water to make drinking water.