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Materials science introduction questions
1. Elemental copper does occur in nature, but copper is mainly extracted from its sulfide, carbonate or oxide minerals. Tin does not occur naturally in the elemental state. The main ore of tin is cassiterite,...
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R3.4 (AHL) Electron-pair sharing reactions
This large AHL sub-topic covers Lewis acids and bases and the formation of coordination bonds. This is followed by considering the role of nucleophiles in organic substitution reactions, where the rate...
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R3.4 Electron-pair sharing reactions
This section concerns the movement of electron pairs which can be represented by curly arrows. Nucleophiles donate an electron pair to form a new bond, as another bond breaks heterolytically producing...
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R3.3 Electron sharing reactions
This section looks at the formation and reactivity of free radicals formed by the homolytic fission of covalent bonds by ultraviolet light. The initiation, propagation and termination steps for the substitution...
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R3.2 Organic redox reactions
This sub-topic concerns the redox reactions of organic compounds. It includes the deduction of the products of oxidation of primary and secondary alcohols (including the two-step oxidation of primary...
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R3.2 (AHL) Electrochemical cells
This AHL section on electrochemical cells includes the standard hydrogen electrode leading to the standard electrode potentials of half-cells. These values are used to obtain the redox reaction that occurs...
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R3.2 Electrochemical cells
The chemistry of primary and secondary (rechargeable) voltaic cells are covered in this section which also covers the electrolysis of molten electrolytes in electrolytic cells. Voltaic cells involves...
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R3.2 Oxidation & reduction
Oxidation and reduction are considered in terms of loss or gain of electrons. Half-equations show the separate processes taking place in acid or neutral solutions and also show the increase in oxidation...
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R3.1 (AHL) Buffer solutions
This section covers the chemistry of buffer solutions. It describes how they can resist a change in pH when small amounts of an acid or alkali are added to the solution or when the solution is diluted....
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R3.1 (AHL) Salt hydrolysis, pH titration curves and indicators
This AHL section explains why the pH of a salt (i.e. whether it is neutral, acidic or basic in aqueous solution) depends on the relative strengths of the parent acid and base. The characteristic shapes...