NPK fertilisers

Ammonia is produced in the Haber process.

The word equation for the reaction to produce ammonia is:

Draw one line from each element to a source of that element.

Ammonia is a gas at room temperature.

Figure 3 shows how ammonia is produced from nitrogen and hydrogen.

Which process takes place at X in Figure 3 ?

Tick () one box.

Complete the sentence.

Use Figure 3.

Table 1 shows the world production of ammonia between 1990 and 2020.

How did the world production of ammonia change between 1990 and 2020?

Use Table 1.

Determine the mean change in mass of ammonia produced per year between 2000 and 2020.

Use Table 1 and the equation:

Most of the ammonia produced in the Haber process is used to make fertilisers.

Which is a reason for the change in the world production of ammonia shown in Table 1 ?

Tick () one box.

Fertilisers produced using ammonia contain nitrogen.

Which two compounds used in fertilisers contain nitrogen?

Use the periodic table.

Tick () two boxes.

This question is about ammonia and nitric acid.

In the Haber process ammonia is produced from nitrogen and hydrogen.

Figure 10 represents the Haber process.

Pipe P links the condenser to the reactor.

Why is the condenser linked to the reactor?

Use Figure 10.

Which metal is used as a catalyst in this reaction?

Nitric acid is produced by reacting ammonia with oxygen.

The word equation for the production of nitric acid is:

ammonia + oxygen → water + nitric acid

Platinum is a catalyst in this reaction.

Describe the test for oxygen gas.

Give the result if oxygen gas is present.

Figure 11 represents the reaction profile of the catalysed reaction between ammonia and oxygen.

Complete the reaction profile for the catalysed reaction in Figure 11.

You should:

label the activation energy

label the reactants and products, using the names of the reactants and products.

How would Figure 11 be different if no catalyst was used?

Tick (✓) one box.

Ammonia and nitric acid react to produce the salt, ammonium nitrate.

Ammonium ions and nitrate ions both contain nitrogen.

Suggest one use of ammonium nitrate.

This question is about ammonia and nitric acid.

In the Haber process ammonia is produced from nitrogen and hydrogen.

Figure 1 represents the Haber process.

Pipe P links the condenser to the reactor.

Why is the condenser linked to the reactor?

Use Figure 1.

Which metal is used as a catalyst in this reaction?

Nitric acid is produced by reacting ammonia with oxygen.

The word equation for the production of nitric acid is:

ammonia + oxygen → water + nitric acid

Platinum is a catalyst in this reaction.

Describe the test for oxygen gas.

Give the result if oxygen gas is present.

Figure 2 represents the reaction profile of the catalysed reaction between ammonia and oxygen.

Complete the reaction profile for the catalysed reaction in Figure 2.

You should:

label the activation energy

label the reactants and products, using the names of the reactants and products.

How would Figure 2 be different if no catalyst was used?

Tick (✓) one box.

Ammonia and nitric acid react to produce the salt, ammonium nitrate.

Ammonium ions and nitrate ions both contain nitrogen.

Suggest one use of ammonium nitrate.

This question is about fertilisers. Compounds of nitrogen (N), phosphorus (P) and potassium (K) are used as fertilisers to improve agricultural productivity. Table 4 shows information about three compounds, A, B and C, that can be used as fertilisers.

A scientist analysed the percentages of nitrogen, phosphorus and potassium in a soil. The percentages of nitrogen and of potassium in the soil were lower than the percentages needed for high agricultural productivity. There was sufficient phosphorus in the soil for high agricultural productivity. Evaluate the use of the compounds in Table 4 to improve the agricultural productivity of this soil.

How is potassium chloride (compound A) obtained from the Earth?

Name one other compound that could be used instead of potassium chloride (compound A) to give a similar improvement in agricultural productivity.

Nitric acid is needed to produce ammonium nitrate (compound B). Name a compound needed to produce nitric acid.

Phosphate rock contains phosphorus compounds. Plants absorb phosphorus from compounds dissolved in rainwater. Suggest why phosphate rock cannot be used directly as a fertiliser.

Phosphate rock can be treated with different acids to produce salts useful as fertilisers. Name the salts which are produced by treating phosphate rock with:

• sulfuric acid

• phosphoric acid.

This question is about fertilisers. Ammonium nitrate is a fertiliser containing nitrogen.

Complete the sentence. Choose the answer from the box.

Ammonium nitrate is produced by reacting ammonia with

Ammonium nitrate fertiliser is sold in 600 kg bags. A farmer spreads 40 bags of ammonium nitrate fertiliser on land with an area

Calculate the mass of ammonium nitrate fertiliser spread per m² of land.

A scientist works for a company which makes ammonium nitrate fertiliser. The scientist investigates the effect of different fertilisers on crop growth. The scientist concludes that the ammonium nitrate fertiliser improves crop growth more than other fertilisers. Suggest one reason why this conclusion might not be valid.

A different fertiliser containing nitrogen has the formula K₂NH₄PO₄

How many atoms of nitrogen are in the formula K₂NH₄PO₄?

Nitrogen and potassium in the fertiliser K₂NH₄PO₄ are important for good crop growth. Which other element in the fertiliser K₂NH₄PO₄ is important for good crop growth? Tick (✓) one box.

Some fertilisers are mixtures of different compounds in fixed proportions. What name is given to a mixture of different compounds in fixed proportions?

This question is about fertilisers. Some fertilisers are described as NPK fertilisers because they contain three elements needed for healthy plant growth.

Which two compounds each contain two of these elements? Tick (✓) two boxes.

Rocks containing calcium phosphate are treated with acid to produce soluble salts that can be used as fertilisers. Name the soluble salts produced when calcium phosphate reacts with:

• nitric acid

• phosphoric acid.

Ammonium sulfate is a compound in fertilisers. Ammonium sulfate can be made using an industrial process or in the laboratory. In the industrial process, the following steps are used.

1. React streams of ammonia solution and sulfuric acid together.

2. Evaporate the water by passing the solution down a warm column.

3. Collect dry crystals continuously at the bottom of the column.

In the laboratory, the following steps are used.

1. React ammonia solution and sulfuric acid in a conical flask.

2. Evaporate water from the solution until crystals start to form.

3. Leave to cool and crystallise further.

4. Separate the crystals using filtration.

5. Dry the crystals between pieces of filter paper.

Evaluate the two methods for producing a large mass of ammonium sulfate.

This question is about ammonia and fertilisers.

Ammonia is produced from nitrogen and hydrogen.

A catalyst is used to speed up the reaction.

The word equation for the reaction is:

nitrogen + hydrogen ammonia

What does the symbol show about the reaction?

Which catalyst is used when ammonia is produced from nitrogen and hydrogen?

Tick (✓) one box.

Figure 1 shows the reaction profile for the production of ammonia both with a catalyst and without a catalyst.

What is represented by label X ?

Tick (✓) one box.

Ammonia is used to produce fertilisers.

NPK fertilisers contain the elements nitrogen, phosphorus and potassium.

A fertiliser contains:

• 22% phosphorus

• 25% potassium.

Draw a bar chart on Figure 2 to show the percentages of phosphorus and of potassium in this fertiliser.

Why do the percentages of phosphorus and of potassium in this fertiliser not add up to 100%?

Fertilisers help plants grow by adding essential elements to soil.

Table 1 shows the percentages of nitrogen, phosphorus and potassium in four fertilisers, A, B, C and D.

Plants lacking essential elements do not grow well because:

• too little phosphorus can cause slow plant growth

• too little potassium can cause leaves to have brown edges.

Which fertiliser helps prevent slow plant growth and brown leaf edges?

Use Table 1.

Tick (✓) one box.

Which fertiliser has the greatest total percentage of essential elements?

Use Table 1.

Tick (✓) one box.

Hydrogen is a raw material in the Haber process.

Hydrogen is produced from methane.

The word equation for the reaction is:

methane + steam carbon monoxide + hydrogen

How can you tell that the reaction is reversible?

The forward reaction is endothermic.

Name the type of energy change in the reverse reaction.

A nickel catalyst is used in this reaction.

Why is a catalyst used in this reaction?

Tick (✓) two boxes.

The Haber process also uses nitrogen to produce ammonia.

Figure 1 shows how the world production of ammonia changed between 1950 and 2010.

Describe how the world production of ammonia changed between 1950 and 2010.

Most of the ammonia produced is used to make fertilisers.

Why did the world production of ammonia change between 1950 and 2010?

Tick (✓) two boxes.

Table 1 shows data about four fertilisers, A, B, C and D.

Which combination of fertilisers A, B, C and D provides all of the elements needed for an NPK fertiliser?

Use Table 1.

Tick (✓) one box.

Which fertiliser is not made using ammonia?

Use Table 1.

Tick (✓) one box.

This question is about reversible reactions and equilibrium.

Hydrogen is used to produce ammonia in the Haber process.

The hydrogen is made in two stages.

Stage 1 is the reaction of methane and steam to produce carbon monoxide and hydrogen.

The equation for the reaction is:

Calculate the atom economy for the formation of hydrogen in stage 1.

Relative atomic masses (A_r): H = 1 C = 12 O = 16

Explain why a low pressure is used in stage 1.

Give your answer in terms of equilibrium.

Stage 2 uses the carbon monoxide produced in stage 1.

The carbon monoxide is reacted with more steam to produce carbon dioxide and more hydrogen.

The equation for the reaction in stage 2 is:

What is the effect of increasing the pressure on the equilibrium yield of hydrogen in stage 2 ?

Figure 10 shows the percentage yield of ammonia produced at different temperatures and pressures in the Haber process.

A temperature of 450 °C and a pressure of 200 atmospheres are used in the Haber process.

A student suggested that a temperature of 350 °C and a pressure of 285 atmospheres could be used instead of those used in the Haber process.

Determine how many times greater the percentage yield of ammonia obtained would be.

Use Figure 10.

A pressure of 285 atmospheres is not used in the Haber process instead of 200 atmospheres.

Give one reason why.

How does Figure 10 show that the forward reaction in the Haber process is exothermic?

World production of ammonia is now about 30 times greater than it was in 1950.

Suggest why the demand for ammonia has increased.