The Haber process

This question is about ammonia.

Ammonia is a gas.

Suggest why the litmus paper used to test for ammonia gas has to be damp.

Ammonia can be made on an industrial scale using the Haber process.

The equation for the reaction is

The reaction can reach a dynamic equilibrium.

Explain what happens when the reaction reaches dynamic equilibrium

Figure 8 shows the changes in percentage yield of ammonia at equilibrium as temperature increases, at a pressure of 300 atmospheres and at a pressure of 1000 atmospheres.

Which row of the table will give the highest percentage yield of ammonia at equilibrium?

In industry, a pressure of 200 atmospheres is used for the Haber process.

Using Figure 8, explain what happens to the position of dynamic equilibrium if the process is carried out at 100 atmospheres.

Ammonia can also be made by heating ammonium chloride.

A sample of solid ammonium chloride is heated in a boiling tube.

After a few minutes ammonium chloride, a white solid, is also seen at the top of the boiling tube, as shown in Figure 9.

Explain how ammonium chloride is formed at the top of the boiling tube.

Ammonia is manufactured in the Haber process by the reversible reaction between nitrogen and hydrogen.

Write the balanced equation for the reversible reaction between nitrogen and hydrogen to make ammonia, NH₃.

Which row shows the typical conditions of temperature and pressure used in the Haber process?

In the Haber process, iron is added to the vessel where the nitrogen and hydrogen react.

State the purpose of the iron.

The reaction between nitrogen and hydrogen to make ammonia can reach dynamic equilibrium.

The reaction gives out heat.

Explain how the position of equilibrium changes if the temperature is decreased.

Compound A is a dark brown gas.

Compound B is a colourless gas.

Two molecules of A combine to form one molecule of B in a reversible reaction.

You are given

• a sealed glass tube containing an equilibrium mixture of A and B

• a beaker

• a kettle

• some ice

At room temperature, the equilibrium mixture is a pale brown colour.

Devise an experiment to show how the position of equilibrium of this reaction is affected by temperature.

The sealed tube must not be opened.

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.

Ammonia is made by reacting nitrogen with hydrogen.

The nitrogen and hydrogen are obtained from raw materials.

Draw one straight line from each gas to the raw material it is obtained from.

When nitrogen and hydrogen are reacted together, the reaction can reach a dynamic equilibrium.

Use words from the box to complete the sentences about dynamic equilibrium.

In a dynamic equilibrium two reactions occur at the same time.

These are the forward reaction and the_........ reaction.

The rates of the two reactions are_........ .

The reaction between nitrogen and hydrogen happens at a pressure of 200 atmospheres.

Another unit of pressure is Pascals, Pa (1 atmosphere = 101 325 Pa).

Calculate the value of 200 atmospheres in Pascals.

Figure 5 shows molecules of nitrogen, hydrogen and ammonia before the reaction and at equilibrium.

Complete the table showing

• the number of hydrogen molecules before reaction

• the number of hydrogen molecules at equilibrium

• the change in the number of hydrogen molecules.

Complete the equation for this reaction.

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.

Many metals corrode.

When a metal corrodes

An experiment is carried out to see if magnesium ribbon wrapped around a piece of iron rod has an effect on the rate at which the iron rod rusts.

The apparatus is shown in Figure 4.

The method used is

• an iron rod, with magnesium ribbon wrapped around it, is placed in a boiling tube labelled A

• 10 cm³ water from a measuring cylinder is poured into this boiling tube

• an identical rod but with no magnesium ribbon wrapped around it is placed in a second boiling tube labelled B

• 10 cm³ water from a measuring cylinder is poured into this boiling tube.

Both boiling tubes are left for a few days.

Explain why iron rod rather than stainless steel rod is used in this experiment.

State why it is not necessary to use a pipette to measure out 10 cm³ water in this experiment.

After a few days the two boiling tubes were examined.

The results are shown in Figure 5.

Explain the results of this experiment.

Hydrazine, N₂H₄, reacts with oxygen.

A metal in water corrodes faster than an identical piece of metal in the same volume of water containing dissolved hydrazine.

Use the information to explain how hydrazine slows corrosion.

Ammonia is used to make hydrazine.

In the industrial process to manufacture ammonia, nitrogen and hydrogen are combined in the presence of an iron catalyst.

State the name of the industrial process to manufacture ammonia.

Predict the effect that adding the catalyst has on the rate of attainment of equilibrium.

Predict the effect that adding the catalyst has on the equilibrium yield of ammonia.

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.

The industrial production of sulfuric acid involves several steps.

One of these steps is the reaction of sulfur dioxide, SO₂, with oxygen to form sulfur trioxide, SO₃.

What volume of sulfur trioxide, in dm³, is produced by the complete reaction of 750 dm³ of sulfur dioxide? (all volumes of gases are measured under the same conditions of temperature and pressure)

Calculate the volume of oxygen needed to react completely with 750 dm³ of sulfur dioxide. (all volumes of gases are measured under the same conditions of temperature and pressure)

Calculate the mass, in kilograms, of 750 dm³ of sulfur dioxide, measured at room temperature and pressure. (relative formula mass: SO₂ = 64; 1 mol of any gas at room temperature and pressure occupies 24 dm³)

*(d) The reaction to produce sulfur trioxide reaches an equilibrium.

The forward reaction is exothermic. The rate of attainment of equilibrium and the equilibrium yield of sulfur trioxide are affected by pressure and temperature.

A manufacturer considered two sets of conditions, A and B, for this reaction. In each case sulfur dioxide is mixed with excess oxygen. The manufacturer changed the temperature and the pressure and only used a catalyst in B. The sets of conditions A and B are shown in Figure 7.

The manufacturer chooses set of conditions B rather than set of conditions A.

Explain, by considering the effect of changing the conditions on the rate of attainment of equilibrium and on the equilibrium yield of sulfur trioxide, why the manufacturer chooses the set of conditions B rather than the set of conditions A.

Covalent substances can be simple molecular covalent or giant covalent.

Ammonia is a simple molecular, covalent substance.

Which is the most likely set of properties for ammonia?

Ammonia, NH₃, is made by reacting nitrogen with hydrogen.

Write the balanced equation for this reaction.

Oxygen, O₂, is also a simple molecular, covalent substance.

Draw a dot and cross diagram for the molecule of oxygen.

*(c) Figure 8 shows the arrangement of carbon atoms in diamond, graphene and a fullerene (C₆₀).

Consider these three substances.

Explain, in terms of their structures and bonding, their relative melting points, strengths and abilities to conduct electricity.