In alkaline solution, $$$\mathrm{MnO}_{4}^{-}$$$ions oxidise $$$\mathrm{SO}_{3}{ }^{2-}$$$ ions to $$$\mathrm{SO}_{4}{ }^{2-}$$$ ions. The $$$\mathrm{MnO}_{4}^{-}$$$ions are reduced to $$$\mathrm{MnO}_{2}$$$. What is the ratio of the two ions in the balanced chemical equation for this reaction?

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_w24_qp_11 Year：2024 Question No：11

Answer:

Knowledge points:

6.1.1 calculate oxidation numbers of elements in compounds and ions

6.1.2 use changes in oxidation numbers to help balance chemical equations

6.1.3 explain and use the terms redox, oxidation, reduction and disproportionation in terms of electron transfer and changes in oxidation number

6.1.4 explain and use the terms oxidising agent and reducing agent

6.1.5 use a Roman numeral to indicate the magnitude of the oxidation number of an element

7.1.1.1 understand what is meant by a reversible reaction

7.1.1.2 understand what is meant by dynamic equilibrium in terms of the rate of forward and reverse reactions being equal and the concentration of reactants and products remaining constant

7.1.1.3 understand the need for a closed system in order to establish dynamic equilibrium

7.1.10 describe and explain the conditions used in the Haber process and the Contact process, as examples of the importance of an understanding of dynamic equilibrium in the chemical industry and the application of Le Chatelier’s principle

7.1.2 define Le Chatelier’s principle as: if a change is made to a system at dynamic equilibrium, the position of equilibrium moves to minimise this change

7.1.3 use Le Chatelier’s principle to deduce qualitatively (from appropriate information) the effects of changes in temperature, concentration, pressure or presence of a catalyst on a system at equilibrium

7.1.4 deduce expressions for equilibrium constants in terms of concentrations,

7.1.5 use the terms mole fraction and partial pressure

7.1.6 deduce expressions for equilibrium constants in terms of partial pressures,

7.1.7 use the expressions to carry out calculations (such calculations will not require the solving of quadratic equations)

7.1.8 calculate the quantities present at equilibrium, given appropriate data

7.1.9 state whether changes in temperature, concentration or pressure or the presence of a catalyst affect the value of the equilibrium constant for a reaction

Answer:

Knowledge points:

Solution:

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