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Edexcel IAL Chemistry 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.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
AS

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.

Covered syllabus points

8.1—What is meant by the term ‘oxidation number’ and understand the rules for assigning oxidation numbers8.2—The oxidation number of elements in compounds and ions8.3—Indicate the oxidation number of an element in a compound or an ion8.4—Write formulae given oxidation numbers8.5—Oxidation and reduction in terms of electron transfer and changes in oxidation number, and the application of these ideas8.6—Oxidising agents gain electrons and reducing agents lose electrons8.7—A disproportionation reaction involves an element in a single species being simultaneously oxidised and reduced8.8—Oxidation number is a useful concept in terms of the classification of reactions as redox and as disproportionation8.9—Metals, in general, form positive ions by loss of electrons with an increase in oxidation number whereas non-metals8.10—Write ionic half-equations and use them to construct full ionic equations 8B: The elements of Groups 1 and 2 Students will8.11—Reasons for the trend in ionisation energy down Groups 1 and 28.12—Reasons for the trend in reactivity of the elements down Group 1 (Li to K) and Group 2 (Mg to Ba)8.13—The reactions of the elements of Group 1 (Li to K) and Group 2 (Mg to Ba) with oxygen, chlorine and water8.14—The reactions of: i oxides of Group 1 and 2 elements with water and dilute acid ii hydroxides of Group 1 and 2 elements8.15—The trends in solubility of the hydroxides and sulfates of Group 2 elements8.16—The reasons for the trends in thermal stability of the nitrates and the carbonates of the elements in Groups 1 and 28.17—The formation of characteristic flame colours by Group 1 and 2 compounds in terms of electron transitions Students will be8.18—Experimental procedures to show: i patterns in the thermal decomposition of Group 1 and 2 nitrates and carbonates Students8.19—Reactions8.20—Solution concentrations, in mol dm-3 and g dm-38.21—CORE PRACTICAL 3 Finding the concentration of a solution of hydrochloric acid8.22—How to minimise the sources of measurement uncertainty in volumetric analysis and estimate the overall uncertainty in8.23—CORE PRACTICAL 4 Preparation of a standard solution from a solid acid and use it to find the concentration of a solution8.24—Reasons for the trends for Group 7 elements in: i melting and boiling temperatures and physical state at room temperature ii8.25—The trend in reactivity of Group 7 elements in terms of the redox reactions of Cl2, Br2 and I2 with halide ions in aqueous8.26—Understand, in terms of changes in oxidation number, the following reactions of the halogens: i oxidation reactions8.27—The following reactions: i solid Group 1 halides with concentrated sulfuric acid, to illustrate the trend in reducing8.28—Make predictions about fluorine and astatine and their compounds, in terms of knowledge of trends in halogen chemistry

Topic 8: Redox Chemistry and Groups 1, 2 and 7 question 1

[Maximum number: 4]

Chlorine dioxide, ClO2\mathrm{ClO}_{2}, can be used to treat water to make it safe for drinking. The molecule is a free radical. One suggested structure is shown.

Figure for Question Topic 8: Redox Chemistry and Groups 1, 2 and 7 question 1 — Edexcel A-Level Chemistry AS

Question (a)

(a)

Chlorine dioxide can be made from potassium chlorate(V), KClO3\mathrm{KClO}_{3}, in a two-step process.

Step 1 Potassium chlorate(V) reacts with concentrated sulfuric acid to form compound A.

Step 2 Compound A then undergoes a disproportionation reaction to form chlorine dioxide and hydrogen chlorate(VII), HClO4\mathrm{HClO}_{4}.

[ 4 ]

Question (i)

(i)

State the meaning of the Roman numerals in chlorate(V) and chlorate(VII).

[ 1 ]

Question (ii)

(ii)

State the oxidation number of chlorine in chlorine dioxide.

[ 1 ]

Question (iii)

(iii)

In Step 2, compound A undergoes disproportionation. Deduce the possible range of oxidation numbers for the chlorine in compound A. Justify your answer.

[ 2 ]

Topic 8: Redox Chemistry and Groups 1, 2 and 7 question 2

[Maximum number: 1]

What is the formula of barium(II) ferrate(VI)?

A

Ba2FeO3\mathrm{Ba}_{2} \mathrm{FeO}_{3}

B

BaFeO3\mathrm{BaFeO}_{3}

C

Ba2FeO4\mathrm{Ba}_{2} \mathrm{FeO}_{4}

D

BaFeO4\mathrm{BaFeO}_{4}

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