Question 2
[Maximum number: 1]
How does an oxidising agent change during a redox reaction?
□ A
□ B
□ C
□ D
(Total for Question 2 = 1 mark)
Edexcel IAL Chemistry AS Topic 8 Redox Chemistry and Groups 1, 2 and 7
Edexcel IAL Chemistry AS Topic 8 Redox Chemistry and Groups 1, 2 and 7
Move between oxidation numbers, half-equations and ionic equations, then connect group trends or qualitative tests to the exact species, reagent and observation given.
Exam points
- Assign oxidation numbers and use their changes to identify oxidation, reduction or disproportionation.
- Construct half-equations and balanced ionic equations with correct electrons, charges and states.
- Apply Group 1, 2 and 7 trends or tests using named reagents, products and observations.
- 8.1—What is meant by the term ‘oxidation number’ and understand the rules for assigning oxidation numbers
- 8.2—The oxidation number of elements in compounds and ions
- 8.3—Indicate the oxidation number of an element in a compound or an ion
- 8.4—Write formulae given oxidation numbers
- 8.5—Oxidation and reduction in terms of electron transfer and changes in oxidation number, and the application of these ideas
- 8.6—Oxidising agents gain electrons and reducing agents lose electrons
- 8.7—A disproportionation reaction involves an element in a single species being simultaneously oxidised and reduced
- 8.8—Oxidation number is a useful concept in terms of the classification of reactions as redox and as disproportionation
Question 5
[Maximum number: 2]
A small piece of calcium is added to a beaker of distilled water.
Question 5(a)
(a)
Which is the equation for this reaction?
□
A
□
B
□
C
□
D
Question 5(b)
(b)
Which element is oxidised and which is reduced when calcium reacts with water?
□ A
□ B
□ C
□ D
(Total for Question 5 = 2 marks)
Question 7
[Maximum number: 1]
The presence of ammonium ions in a compound can be shown by adding a reagent, warming the mixture and testing the gas evolved.
What is the reagent and the result of the test for the gas evolved?
□ A
□ B
□ C
□ D
(Total for Question 7 = 1 mark)
Question 8
[Maximum number: 1]
Aqueous chlorine is added to an aqueous solution of potassium iodide.
A non-polar organic solvent is then added and the mixture is shaken.
The layers are allowed to separate.
What colour is seen in the organic layer?
A
brown
B
green
C
orange
D
violet
Question 9
[Maximum number: 3]
A titration is carried out by adding dilute sulfuric acid from a burette to aqueous sodium hydroxide in a conical flask. The indicator is methyl orange.
Question 9(a)
(a)
What is the colour change of the indicator at the end-point of this titration?
A
red to orange
B
red to yellow
C
yellow to orange
D
yellow to red
[ 1 ]
Question 9(b)
(b)
A student carried out the first titration and did not notice that there was an air bubble between the tap and the tip of the burette.
During the titration, the air bubble filled with acid.
The student then carried out two accurate titrations in which there was no air bubble in the burette. There were no other errors in these titrations.
Which of these could be the three titres for this student?
□ A
□ B
□ C
□ D
[ 1 ]
Question 9(c)
(c)
of aqueous sodium hydroxide required a mean titre of of sulfuric acid.
What is the concentration, in , of the sulfuric acid?
A
0.0374
B
0.0668
C
0.134
D
0.267
[ 1 ]
Question 15(a)
[Maximum number: 3]
This question is about calcium carbonate, .
Calcium carbonate decomposes on heating.
Explain why calcium carbonate decomposes at a higher temperature than magnesium carbonate, in terms of the charge and size of the cations.
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Question 16
[Maximum number: 4]
This question is about the halogens and some of their compounds.
Question 16(a)
(a)
Descending the group from fluorine to iodine, the electronegativity of the atoms decreases even though their nuclear charge increases.
Explain the trend in electronegativity.
(2)
[ 2 ]
Question 16(b)
(b)
lodate(V) ions, , react with iodide ions in acid solution.
Explain, in terms of the oxidation numbers of iodine in the three species, why this is not a disproportionation reaction.
[ 2 ]
Question 16(c)
(c)
Hydrogen bromide and hydrogen iodide reduce sulfuric acid.
Identify, by name or formula, the compound produced containing sulfur with its lowest oxidation number in that reaction.
