The effect of changing conditions on equilibrium

This question is about methanol.

Methanol is used in screenwash.

Screenwash is used to keep car windscreens clean.

Screenwash is a formulation.

Define the term ‘formulation’.

Carbon monoxide and hydrogen are used to produce methanol.

The conditions used in the production of methanol are:

• high temperature

• high pressure

• a catalyst.

The equation for the reaction is:

91 kJ/mol of energy is transferred during the exothermic forward reaction.

How much energy is transferred when methanol is decomposed into carbon monoxide and hydrogen?

Tick () one box.

A scientist developed a principle to predict the effect of changing conditions on a system at equilibrium.

What was the name of the scientist?

What is the effect of increasing the temperature on the proportion of methanol in the equilibrium mixture?

Tick () one box.

What is the effect of using a catalyst on the proportion of methanol in the equilibrium mixture?

Tick () one box.

Explain the effect of increasing the pressure on the proportion of methanol in the equilibrium mixture.

Explain the effect of using a catalyst on the rate of production of methanol.

The catalyst allows the reaction to take place at a lower temperature.

Explain one advantage of using a lower temperature in the production of methanol.

Do not refer to the position of equilibrium in your answer.

Methanol (CH₃OH) can also be produced by reacting carbon dioxide with hydrogen.

Water is the other product of the reaction.

Write a balanced equation for the reaction.

Sulfuric acid is produced by an industrial process.

In the process, sulfur dioxide (SO₂) reacts with oxygen (O₂) to produce

The equation for the reversible reaction is:

The forward reaction releases 198 kJ/mol of energy.

What is the amount of energy transferred during the reverse reaction?

Tick () one box.

The concentration of oxygen is increased.

What is the effect on the position of the equilibrium?

Tick () one box.

The pressure is decreased.

What is the effect on the position of the equilibrium?

Tick () one box.

The temperature is increased.

What is the effect on the position of the equilibrium?

Tick () one box.

A catalyst is used in the reaction.

Suggest what effect the catalyst has on the position of the equilibrium.

Give one reason for your answer.

A scientist measured how the number of moles of sulfur dioxide, oxygen and

sulfur trioxide varied with time during the reaction.

Figure 5 shows the results.

Determine the time taken for the reaction to reach equilibrium.

Explain your answer.

Use Figure 5.

Figure 6 shows the results for sulfur trioxide.

Determine the rate of reaction at 60 seconds.

Some types of water contain dissolved substances.

A student investigated the mass of dissolved solids in distilled water and in sea water. Figure 1 shows the apparatus.

This is the method used.

1. Weigh an evaporating basin.

2. Add 20 cm³ of distilled water to the evaporating basin.

3. Weigh the evaporating basin and the water sample.

4. Heat the water sample for 2 minutes.

5. Weigh the evaporating basin and contents.

6. Repeat steps 1 to 5 two more times.

7. Repeat steps 1 to 6 with sea water.

The method used by the student did not give valid results. Describe one improvement the student could make to obtain valid results.

A different student used a method which gave valid results.

Table 2 shows the results.

Calculate the value X for the mass of dissolved solids in sea water in Test 2.

The student concludes that distilled water is pure. Describe a test to confirm that distilled water is pure.

Tap water is potable.

A stage in the production of potable water is sterilising. A gas is used to sterilise water. The equation for the reaction is:

What is meant by the symbol ?

The reaction is at equilibrium. The reaction is exothermic. What happens to the equilibrium position when the temperature is increased? Tick (✓) one box.

Describe a test to identify the gas used to sterilise water.

Another stage in the production of potable water is filtering. Explain why potable water contains dissolved solids after filtering.

This question is about catalysts and equilibrium.

What type of substance is a catalyst in biological systems? Tick (✓) one box.

Explain how a catalyst increases the rate of a reaction.

The reversible reaction for the production of ammonia is:

What can scientists predict using Le Chatelier’s Principle?

Describe how a reversible chemical reaction is able to reach equilibrium.

Explain the effect of increasing the pressure on the yield of ammonia.

The forward reaction to produce ammonia is exothermic. Explain the effect of increasing the temperature on the yield of ammonia.

Ammonia is produced when a mixture of nitrogen and hydrogen reacts.

The equation for the reaction is:

Nitrogen is obtained from the air.

The mixture of nitrogen and hydrogen must not contain carbon dioxide and oxygen.

Explain how a sample can be tested to show that carbon dioxide is not present in the mixture.

A catalyst is used in the reaction.

Explain how a catalyst increases the rate of a reaction.

The equation for the reaction to produce ammonia is repeated here.

The reaction reaches equilibrium.

Explain how an equilibrium is reached.

Suggest how the catalyst affects the equilibrium position.

Give one reason for your answer.

What is the effect of increasing the pressure on the reaction to produce ammonia?

Tick (✓) one box.

The forward reaction is exothermic.

Explain the effect of increasing the temperature on the yield of ammonia gas produced at equilibrium.

This question is about equilibrium.

Describe how a reaction reaches equilibrium.

Nitrogen dioxide gas reacts to form dinitrogen tetraoxide gas. The reaction is reversible. The equation for the reaction is:

Explain the effect on the equilibrium position of increasing the pressure.

Figure 7 shows the change in the percentage of dinitrogen tetroxide (N₂O₄) in the equilibrium mixture as the temperature of the equilibrium mixture is changed.

Explain the effect on the equilibrium position of increasing the temperature. Use Figure 7.

This question is about oxygen (O₂) and sulfur dioxide (SO₂).

Give the test and result for oxygen gas.

The reaction between oxygen and sulfur dioxide is at equilibrium.

Some of the sulfur trioxide (SO₃) is removed. Explain what happens to the position of the equilibrium.

Sulfur dioxide is an atmospheric pollutant. Sulfur dioxide pollution is reduced by reacting calcium oxide with sulfur dioxide to produce calcium sulfite.

7.00 g of calcium oxide reacts with an excess of sulfur dioxide. Relative atomic masses (A_r): O = 16 S = 32 Ca = 40 Calculate the mass of calcium sulfite produced.

Bleach is a solution of sodium hypochlorite (NaClO). Chlorine gas is produced when bleach reacts with hydrochloric acid. NaClO(aq) + 2HCl (aq) NaCl(aq) + H₂O(l) + Cl₂(g)

Give the test and result for chlorine gas.

Figure 8 shows a sealed flask of sodium hypochlorite and hydrochloric acid at equilibrium.

Explain why equilibrium is reached in this reaction.

The stopper in Figure 8 is removed and hydrochloric acid is added. The stopper is replaced. Explain what happens to the equilibrium.

Chlorine gas is also produced when hydrogen chloride decomposes.

The forward reaction is endothermic.

Predict the effect of increasing the temperature on the amount of chlorine gas produced at equilibrium. Explain your answer using Le Chatelier’s Principle.

Explain the effect of increasing the pressure on this equilibrium.