Redox (Cambridge (CIE) IGCSE Combined Science: Chemistry): Flashcards
Exam code: 0653
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What is oxidation in terms of oxygen? (Extended Tier Only)
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What is oxidation in terms of oxygen? (Extended Tier Only)
Oxidation is the gain of oxygen by an element or compound.
For example, carbon is oxidised when it gains oxygen to form carbon dioxide.
What is reduction in terms of oxygen? (Extended Tier Only)
Reduction is the loss of oxygen from an element or compound.
For example, zinc oxide is reduced when it loses oxygen to form zinc metal.
True or False?
In a redox reaction, oxidation and reduction occur simultaneously. (Extended Tier Only)
True.
A redox reaction always involves both oxidation and reduction happening at the same time in the same reaction. One species gains oxygen while another loses it.
In the reaction between zinc oxide and carbon, zinc oxide .......... (gains/loses) oxygen so it is reduced, while carbon .......... oxygen so it is oxidised. (Extended Tier Only)
In the reaction between zinc oxide and carbon, zinc oxide loses oxygen so it is reduced, while carbon gains oxygen so it is oxidised.
What do Roman numerals in a compound's name indicate? (Extended Tier Only)
Roman numerals indicate the oxidation number (charge) of the transition metal ion in the compound.
For example, iron(III) oxide contains Fe3+ ions and iron(II) oxide contains Fe2+ ions.
State the formula of iron(III) oxide. (Extended Tier Only)
The formula of iron(III) oxide is Fe2O3.
It contains iron(III) ions, Fe3+, meaning the oxidation number of iron is 3.
True or False?
In the reaction Fe2O3 + 3CO → 2Fe + 3CO2, carbon monoxide is reduced. (Extended Tier Only)
False.
Carbon monoxide gains oxygen to form carbon dioxide, so it is oxidised. Iron(III) oxide loses oxygen to form iron, so it is reduced.
Iron can form two types of ion: Fe2+ is called .......... and Fe3+ is called .......... . (Extended Tier Only)
Iron can form two types of ion: Fe2+ is called iron(II) and Fe3+ is called iron(III).
In the reaction between iron(III) oxide and carbon monoxide, identify which substance is oxidised and which is reduced. (Extended Tier Only)
Iron(III) oxide is reduced because it loses oxygen to form iron. Carbon monoxide is oxidised because it gains oxygen to form carbon dioxide.
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