Exam code: J248
Look at the equation for the Haber process.
N2 + 3H2 ⇌ 2NH3
What is meant by the symbol ⇌ in the equation?
A reaction that involves a catalyst.
A reaction that is exothermic
A reaction with 100% atom economy.
A reversible reaction.
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Which statement is true for a reversible reaction when it is at dynamic equilibrium?
The concentration of the products is increasing.
The rate of the backward reaction is greater than the rate of the forward reaction.
The rate of the forward reaction is equal to the rate of the backward reaction.
The rate of the forward reaction is greater than the rate of the backward reaction.
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Ammonia is made in the Haber process.
N2 + 3H2 2NH3
What happens when this reaction reaches equilibrium?
The backward reaction happens at a faster rate than the forward reaction.
The forward and backward reactions happen at the same rate.
The forward and backward reactions stop happening.
The forward reaction happens at a faster rate than the backwards reaction.
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The diagram shows a test tube containing ammonium chloride that has been heated gently.
Which two gases are present at position Y?
ammonia and hydrogen chloride
ammonia and chlorine
hydrogen and chlorine
ammonia and hydrogen
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When hydrogen gas is heated with iodine gas, hydrogen iodide gas is produced.
The equation for this reversible reaction is:
hydrogen + iodine ⇌ hydrogen iodide
This reversible reaction reaches equilibrium in a sealed container.
Which of the following statements is correct?
The forward reaction and reverse reaction are both exothermic.
The mass of each substance does not change.
The hydrogen no longer reacts with iodine.
The gases have escaped from the container.
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The Haber process is an example of a reversible reaction where the forward reaction is exothermic:
N2 (g) + 3H2 (g) 2NH3 (g)
What is not true about this system when it is at equilibrium?
The energy change of the reverse reaction is endothermic
The equilibrium occurs within a closed system
The reaction has reached completion and stopped
The rate of the forward reaction is equal to the rate of the reverse reaction
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Which graph shows the highest yield of products?
All of the above have the same yield of products
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The gasification of carbon is a reversible endothermic reaction:
C (s) + H2O (g) CO (g) + H2 (g)
Which of the following conditions could be changed to increase the relative amount of H2 gas produced?
Increase the surface area to volume ratio of the carbon
Increase the pressure
Increase the temperature
Add a catalyst
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Which statement is not true about Le Chatelier's Principle?
If changes to the conditions of a system are made, the system responds to counteract the change
If the concentration of the product is decreased, more reactants will react until an equilibrium position is reached again
Increasing the pressure will shift the position of the equilibrium to the side with the smaller number of molecules of gas
If temperature is decreased for an exothermic reaction, the relative amount of products made at the equilibrium point decreases
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Hydrogen gas and iodine vapour can react to form hydrogen iodide:
H2 (g) + I2 (g) 2HI (g)
Which statement is not true?
This reaction is reversible
Equal amounts of reactants and product are eventually made at equilibrium
This reaction can reach an equilibrium point in a closed system
There are equal total numbers of moles of reactant and as of product
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Some systems at equilibrium can be studies by changes in colour.
Fe3+ (aq) + SCN- (aq) FeSCN2+ (aq)
yellow colourless red
This reaction starts with only the reactants, and reaches equilibrium at a point where there are equal amounts of Fe3+ and FeSCN2+ present. The solutions used are very dilute.
What colour change would you expect to see during the course of the reaction?
Yellow to orange to red
Yellow to red
Yellow to orange
Yellow to red to orange
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Which option shows two correct statements about reversible reactions and equilibrium?
| Statement 1 | Statement 2 |
A | The sign for a reversible reaction is | Reversible reactions are slower than non-reversible ones |
B | At equilibrium the rate of the forward reaction and the rate of the reverse reaction are equal | An endothermic reaction is exothermic if reversed |
C | Reversible reactions are not useful in industry as they do not go to completion | To reach an equilibrium the reaction must occur in a closed system |
D | The rate of the reaction is zero at equilibrium | The concentration of the product is constant at equilibrium |
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Which statement describes what happens when a reaction reaches equilibrium?
The forward reaction happens at a faster rate than the backwards reaction.
The forward and backward reactions happen at the same rate.
The forward and backward reactions stop happening.
The backward reaction happens at a faster rate than the forward reaction.
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The decomposition of ammonium chloride is endothermic:
NH4Cl (s) NH3 (g) + HCl (g)
Which changes to the conditions would both decrease the amount of product in this reaction?
| Change 1 | Change 2 |
A | Increase pressure | Decrease temperature |
B | Decrease pressure | Decrease temperature |
C | Increase pressure | Increase temperature |
D | Decrease pressure | Increase temperature |
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Look at the equation for a reversible reaction.
4NH3 (g) + 5O2 (g) ⇌ 4NO (g) + 6H2O (g) ΔH = –950 kJ mol–1
The reversible reaction forms a dynamic equilibrium in a sealed container.
Which of the following would move the position of equilibrium to the right?
Decreasing the pressure and decreasing the temperature
Increasing the pressure and decreasing the temperature.
Increasing the pressure and increasing the temperature.
Increasing the pressure and using a catalyst.
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Which graph shows a dynamic equilibrium?
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The reaction for the production of ammonia is shown below.
N2(g) + 3H2(g) 2NH3(g)
What is the effect of increasing pressure on the rate of production of ammonia and the percentage yield of ammonia?
| rate of production | percentage yield |
A | increases | decreases |
B | increases | increases |
C | decreases | increases |
D | decreases | decreases |
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Carbon monoxide and steam react together exothermically to produce the alcohol methanol, as shown in the equation.
CO(g) + 2H2(g) ⇌ CH3OH(g)
Both reactants and the product are gaseous. Which conditions of pressure and temperature would provide the highest yield of CH3OH?
Low pressure and low temperature.
Low pressure and high temperature.
High pressure and low temperature.
High pressure and high temperature.
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