The flow diagram below shows the processes involved in the industrial preparation of fertiliser Q - NSC Physical Sciences - Question 10 - 2016 - Paper 2

Process Y is known as the contact process.

Gas P is sulfur trioxide, which has the chemical formula SO₃.

The balanced equation for the formation of compound B (sulfuric acid) from gas P (sulfur trioxide) is as follows:

$SO₃ + H₂O \rightarrow H₂SO₄$

The balanced chemical equation for the formation of fertiliser Q from compound A (ammonium sulfate) and compound C (water) is:

$H₂SO₄ + 2NH₃ \rightarrow (NH₄)₂SO₄$

In the provided NPK fertiliser:

• Mass of nitrogen (N) = 4.11 kg
• Mass of phosphorus (P) = 0.51 kg
• Let the mass of potassium (K) be denoted as x.

The total mass of fertiliser = 20 kg.

Thus, we have:

$N + P + K = 20$

Substituting the known values: $4.11 + 0.51 + x = 20$

Solving for x:

$x = 20 - (4.11 + 0.51) = 20 - 4.62 = 15.38$

Now calculating the percentage of each component:

Percentage of N = $\frac{4.11}{20} \times 100 = 20.55\%$

Percentage of P = $\frac{0.51}{20} \times 100 = 2.55\%$

Percentage of K = $\frac{15.38}{20} \times 100 = 76.92\%$

Thus, the NPK ratio of the fertiliser is:

N:P:K = 20.55:2.55:76.92.