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Question 1
This question is about reaction profiles and enthalpy. The diagram below shows a typical reaction profile for the decomposition of hydrogen peroxide. |
a) | Which letter represents the activation energy? A B C D
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b) | The decomposition of hydrogen peroxide results in energy being given to the surroundings. What type of reaction is this? A displacement B endothermic C exothermic D neutralisation
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c) | What does arrow C represent? A change in temperature B overall energy change C activation energy D energy of hydrogen peroxide
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Question 2
Butane (C4H10) reacts with oxygen in the air when combusted to form carbon dioxide and water. |
a) | Complete the balanced chemical equation to show the combustion of butane.
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b) | Draw the structure of butane C4H10 to show all the covalent bonds.
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c) | The table below shows the bond energies for the bonds. Calculate the energy to break all the bonds in the reactants.
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d) | Calculate the energy released when all the bonds in the products are formed.
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e) | Calculate the molar enthalpy change (ΔH) in kJ/mol, for the combustion of butane. Include a sign in your answer.
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Question 3
A student is investigating the temperature change during a chemical reaction. This is the method the student used:
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a) | The table below shows how the temperature varied during the reaction. Model answer
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b) | The student repeats the experiment with 5 cm3 of dilute hydrochloric acid. Draw how the temperature would vary with time.
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c) | The temperature increased during the reaction. State whether the reaction is endothermic or exothermic.
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d) | Sketch the reaction profile for the reaction between hydrochloric acid and sodium hydroxide. Your diagram should include:
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Question 4
A student is investigating the energy change when a salt dissolves in water to form a solution. The student's method is given below:
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a) | Explain why the student is using a polystyrene cup instead of pouring the water into a glass beaker.
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b) | The diagram below shows the thermometer before the copper sulfate is added and the maximum temperature reached. Calculate the change in temperature of the copper sulfate solution.
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c) | Calculate the heat energy change (Q) for the reaction between copper sulfate and water. The mass of 1.0 cm3 of water is 1.0 g and the specific heat capacity of water is 4.2 J/g/°C. Give your answer in kJ to 2 decimal places.
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d) | What type of reaction occurred between the copper sulfate and the water? A neutralisation B endothermic C exothermic D displacement
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Question 5
A student is investigating the energy change when a piece of magnesium ribbon is dropped into hydrochloric acid. |
a) | Write a balanced chemical equation for the reaction between magnesium (Mg) and hydrochloric acid (HCl) to form magnesium chloride and hydrogen.
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b) | The reaction results in energy being transferred to the surroundings. Draw a reaction profile for the reaction between magnesium and hydrochloric acid.
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c) | The mass of hydrochloric acid used was 25 g. The student recorded a temperature change of 8 °C. Calculate the energy (Q) transferred due to the reaction. The specific heat capacity of hydrochloric acid is 4.04 J/g/°C.
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Question 6
A student is investigating the energy released when using ethanol in a spirit burner. The diagram below shows the student's apparatus. |
a) | Describe how the student could use the equipment in the diagram to find the heat released per gram of fuel burned.
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b) | The table below shows the student's results. Calculate the energy released by the burner. The specific heat capacity of water is 4.2 J/g/°C.
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c) | Another student calculates their theoretical temperature change to be 35°C. They only recorded a temperature change of 33°C. Suggest why the temperature change recorded may be lower than the theoretical temperature change.
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d) | The table below shows how the molar enthalpy change varies for different alcohols. Describe the relationship between molar enthalpy change and the number of carbon atoms per molecule of fuel.
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Question 7
This question is about the reaction between methane and steam to produce hydrogen. |
a) | Write a balanced symbol equation for the reaction between methane and steam. Include state symbols.
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b) | The table below shows the bond energies for the reaction between methane and steam. Calculate the energy change for the forward reaction.
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c) | Complete the reaction profile for the reaction between methane and steam to form hydrogen and carbon monoxide.
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d) | The reaction is reversible. State the effect of increasing the temperature on the yield of hydrogen.
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Question 8
This question is about the combustion of propane. |
a) | State what is meant by the term activation energy.
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b) | Sketch the structure of propane to show all the covalent bonds.
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c) | Write a balanced symbol equation for the combustion of propane.
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d) | The table below shows the bond energies for the reaction. Calculate the energy change for the reaction and state whether the reaction is endothermic or exothermic.
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Question 9
A student is investigating the reactivity of group 1 metals. The student's method is below:
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a) | State the name of the piece of equipment used to measure temperature.
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b) | Suggest two variables the student would need to control during this investigation.
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c) | The table below shows the student's results. Calculate the temperature rise for the reaction between potassium and water.
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d) | Describe the pattern shown by the student's results and explain how this shows the trend in reactivity as you go down group 1.
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e) | The student draws a reaction profile for the reaction between group 1 metals and water. The reaction profile is incorrect. State two errors in the reaction profile.
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