NPK fertilisers

A student makes some ammonium sulfate solution by using a titration.

Which pair of solutions should be used to make the ammonium sulfate solution?

The student uses the following apparatus to make the solution of ammonium sulfate.

Draw one straight line from each apparatus name to the diagram of the apparatus.

In this titration, the student uses methyl orange as the indicator.

Explain why an indicator is used in a titration.

The student carries out a rough titration first.

Figure 9 shows the burette readings at the start and at the end of the titration.

At the start of the titration, the burette reading is 2.15 cm³.

Give the reading on the burette at the end of the titration.

The student carries out accurate titrations to obtain concordant results.

Figure 10 shows the volume of solution delivered by the burette in the three accurate titrations.

Circle the volumes the student should use to calculate the mean volume.

Using the volumes that you have circled, calculate the mean volume of solution delivered by the burette.

mean volume of solution =_........ cm³

Phosphoric acid is important in the production of fertilisers.

A few drops of litmus solution are added to a sample of dilute phosphoric acid.

What is the colour of the mixture formed?

State why litmus cannot be used to measure pH.

Phosphoric acid can react to form phosphate salts which are used in fertilisers.

Give two reasons why farmers use fertilisers on their fields.

An experiment was carried out to produce phosphoric acid.

The actual yield for the experiment was 18.62 g.

The theoretical yield for the experiment is 24.50 g.

Calculate the percentage yield of this experiment.

percentage yield =_........

The equation for a reaction to make phosphoric acid, H₃PO₄, is

Calculate the atom economy for the production of phosphoric acid in this reaction.

(relative formula masses: Ca₅(PO₄)₃OH = 502, H₂SO₄ = 98, H₃PO₄ = 98, CaSO₄ = 136, H₂O = 18)

atom economy =_........ %

The equation for a reaction to produce phosphoric acid is

Explain how the atom economy of the reaction can be increased.

Nitrogen reacts with hydrogen to form ammonia.

The reaction is reversible.

Complete the word equation for the reaction by adding the symbol to show that the reaction is reversible.

nitrogen + hydrogen_........ ammonia

Figure 4 shows the electronic configuration of an atom of hydrogen.

Complete the dot and cross diagram for a molecule of hydrogen, H₂.

H H

Ammonia reacts with sulfuric acid to form ammonium sulfate.

Write the word equation for this reaction.

Ammonium sulfate contains ammonium ions, NH₄⁺, and sulfate ions, SO₄^2–.

What is the formula of ammonium sulfate?

Explain why some farmers spread ammonium sulfate on their fields.

Figure 10 shows some information on a container of plant fertiliser.

State which element, often present in fertilisers, is not present in this fertiliser.

Ammonium nitrate, NH₄NO₃, is prepared for use in fertilisers by neutralising ammonia with an acid.

Which acid reacts with ammonia to produce ammonium nitrate?

State why farmers spread fertilisers on their fields.

Ammonium sulfate is a fertiliser and is produced on a large scale in industry.

In this process, ammonia reacts with sulfuric acid.

Write the word equation for the reaction between ammonia and sulfuric acid.

Ammonium sulfate can also be made in the laboratory by titrating ammonia solution with dilute sulfuric acid. Give one disadvantage of using this laboratory method to produce ammonium sulfate as a fertiliser compared with an industrial method.

*(c) In the laboratory, ammonium sulfate crystals can be made using ammonia solution and dilute sulfuric acid. The volume of ammonia solution required to neutralise 25 cm³ of dilute sulfuric acid is found by titration using an indicator. The results of the titration can be used to prepare a solution of ammonium sulfate. Pure, dry ammonium sulfate crystals can be made from this solution. Figure 11 shows some of the equipment that may be used in the experiment.

Write a detailed method to make ammonium sulfate crystals starting with ammonia solution and dilute sulfuric acid.

Titration is used to carry out some neutralisation reactions.

Ammonium nitrate can be made by neutralisation.

State the name of the two reactants that are neutralised to make the salt ammonium nitrate.

Ammonium nitrate is a fertiliser. Another fertiliser is ammonium phosphate.

Which elements are combined in ammonium phosphate?

Titrations involve aqueous solutions and the use of burettes.

Figure 8 shows readings on part of a burette at the start and at the end of a titration.

Calculate the volume of solution added from this burette.

Give your answer to a suitable number of decimal places.

A student carries out a titration four times.

The volumes from the student’s results table are shown in Figure 9.

Tick the volumes that should be used to calculate the mean volume.

Figure 10 shows the burette and flask prepared for use by the student. The burette is supported vertically by a clamp that is not shown in the diagram.

The student wrote a description of how they used the burette.

Give three improvements to the way that the student used the burette.

In a titration a student placed alkali in the flask.

By mistake a few drops of litmus and a few drops of phenolphthalein were added to the flask.

The student added acid to the flask until the mixture was acidic.

Predict the colour change that would be seen.

In a titration a student rinsed out the flask with distilled water and did not dry it.

They used the flask for titration, adding the solution from the burette until the indicator changed colour.

State the effect, if any, on the titre volume of using the wet flask rather than a dry flask.

Figure 1 shows a bag of NPK fertiliser.

N, P and K are the symbols of three elements that are essential for plant growth.

N is the symbol for nitrogen.

Name the other two elements, P and K, that are essential for plant growth.

You may want to refer to the periodic table.

Many fertilisers are produced using ammonia.

Ammonia is produced on an industrial scale from the reaction of nitrogen with hydrogen.

The equation for the reaction is

nitrogen + hydrogen ammonia

State the name of this industrial process.

State the meaning of the symbol in the equation.

Figure 2 shows the electronic configurations for an atom of nitrogen and an atom of hydrogen.

Which dot and cross diagram for ammonia, NH₃, is correct?

Ammonia reacts with nitric acid to produce ammonium nitrate.

Write the word equation for this reaction.

The volume of dilute sulfuric acid required to neutralise 25.0 cm³ of ammonia solution can be found by titration.

In the titration, a few drops of methyl orange indicator were added to the ammonia solution in a conical flask before adding the dilute sulfuric acid.

State the change in colour of the methyl orange at the end point when the ammonia solution has just been neutralised.

When the ammonia solution was neutralised by the dilute sulfuric acid, a solution of ammonium sulfate was formed.

Complete the balanced equation for the reaction between ammonia solution and sulfuric acid.

The titration was repeated to obtain a mean volume of dilute sulfuric acid required to neutralise the 25.0 cm³ of ammonia solution. The volumes of the two solutions were measured accurately.

Explain two other practical steps that should be used in the titration to ensure that an accurate titre volume is obtained.

The mean volume of dilute sulfuric acid required to neutralise the ammonia solution was determined from the results of the titration.

This volume of dilute sulfuric acid was added to 25.0 cm³ of ammonia solution in a conical flask.

Devise a plan to produce a sample of dry ammonium sulfate from the contents of the conical flask.

Fertilisers are sometimes added to soil.

State why fertilisers are added to soil.

Fertilisers contain compounds of different elements. Three of these elements have the symbols K, N and P.

Use the periodic table to state the names of these three elements.

The fertiliser ammonium sulfate may be made by titrating ammonia solution with dilute sulfuric acid.

Three pieces of apparatus, P, Q and R, used to measure volumes of liquid are shown in Figure 1.

Give the names of the pieces of apparatus P and Q.

In the titration experiment, small volumes of dilute sulfuric acid are added gradually to the ammonia solution in a flask.

Give the letter, P, Q or R, of the piece of apparatus in Figure 1 that should be used to add the dilute sulfuric acid.

The titration experiment is used to produce a solution of ammonium sulfate.

Describe how solid ammonium sulfate should be obtained from this solution.

In industry, ammonia is manufactured by reacting nitrogen with hydrogen.

Give the name of the industrial process used to manufacture ammonia.

Write the word equation for this reaction, including the correct symbol to show that the reaction is reversible.

The formula of ammonia is NH₃.

State what the formula of ammonia shows about the number of nitrogen atoms and the number of hydrogen atoms combined in a molecule of ammonia.

Most of the ammonia manufactured in industry is used to produce fertilisers.

A fertiliser is made by reacting ammonia with nitric acid.

What is the name of this fertiliser?

Explain the importance of fertilisers in farming.

Ammonia is manufactured by the Haber process.

The equation for the reaction is

The reaction is reversible and can reach equilibrium.

An iron catalyst can be used in the reaction.

Which row of the table shows how adding the iron catalyst affects the rate of attainment of equilibrium and the equilibrium yield of ammonia?

Which of the following statements is correct when the reaction reaches equilibrium?

The reaction is carried out at a pressure of 200 atmospheres.

Explain what effect a pressure higher than 200 atmospheres would have on the rate of attainment of equilibrium and on the equilibrium yield of ammonia.

Ammonium sulfate and ammonium nitrate are used as fertilisers as they both contain nitrogen, which will increase the yield of crops.

Suggest one other reason for using solid ammonium sulfate and solid ammonium nitrate as nitrogenous fertilisers.

Ammonium nitrate can be made by the reaction of ammonia with nitric acid.

Write the balanced equation for this reaction.

(a) Nitric acid can be titrated with a solution of ammonia.

State the type of reaction occurring when nitric acid reacts with ammonia.

What salt is formed in this reaction?

In one stage of the production of nitric acid, nitrogen oxide, NO, is reacted with oxygen to make nitrogen dioxide, NO₂.

Calculate the minimum volume of air, measured at room temperature and pressure, required to react with 1000 g nitrogen oxide to form nitrogen dioxide.

Assume that the air contains 20% oxygen by volume. (relative atomic masses: N = 14, O = 16 1 mol of gas occupies 24 dm³ at room temperature and pressure)

*(c) In another stage in the production of nitric acid, ammonia is reacted with oxygen to form nitrogen oxide and water.

Heat energy is given out when ammonia reacts with oxygen.

The conditions chosen for the reaction are

• excess air, rather than just the right amount

• a pressure of 10 atm, rather than atmospheric pressure

• a temperature of 900 °C, rather than room temperature.

Explain the effect of the conditions chosen on the equilibrium yield of nitrogen oxide and on the rate of attainment of equilibrium.

Figure 1 shows the dot and cross diagram for a molecule of ammonia.

What do the dots and crosses represent in the diagram?

Give the formula for the molecule of ammonia.

Ammonia can be manufactured by the Haber process.

The word equation for the reaction is

nitrogen + hydrogen ammonia

State the meaning of the symbol.

In the Haber process, the percentage yield of ammonia at equilibrium changes with temperature.

Figure 2 shows how the percentage yield of ammonia at equilibrium changes with temperature.

State what happens to the percentage yield of ammonia at equilibrium as the temperature increases.

Use the graph to find the percentage yield of ammonia at equilibrium at 450°C.

Ammonia reacts with nitric acid to form ammonium nitrate.

Complete the word equation for this reaction.

An ammonium ion has the formula NH₄⁺.

A nitrate ion has the formula NO₃^–.

Which of the following is the formula for ammonium nitrate?

Explain why farmers spread ammonium nitrate on their fields.