Redox (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Chemistry): Flashcards
Exam code: 0654 & 0973
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Define oxidation in terms of oxygen.
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Define oxidation in terms of oxygen.
Oxidation is the gain of oxygen by an element or compound during a chemical reaction.
Define reduction in terms of oxygen.
Reduction is the loss of oxygen from an element or compound during a chemical reaction.
In the reaction between zinc oxide and carbon, zinc oxide is .......... because it loses oxygen, while carbon is .......... because it gains oxygen.
In the reaction between zinc oxide and carbon, zinc oxide is reduced because it loses oxygen, while carbon is oxidised because it gains oxygen.
True or False?
In a redox reaction, oxidation and reduction occur in separate reactions at different times.
False.
In a redox reaction, oxidation and reduction occur simultaneously in the same reaction. One species gains oxygen while another loses oxygen at the same time.
What information does the Roman numeral in the name of a transition metal compound provide?
The Roman numeral gives the oxidation number (charge) of the transition metal ion in that compound. For example, iron(III) indicates that the iron ion has a 3+ charge, Fe3+.
Iron(II) oxide has the formula .......... and contains Fe2+ ions, while iron(III) oxide has the formula .......... and contains Fe3+ ions.
Iron(II) oxide has the formula FeO and contains Fe2+ ions, while iron(III) oxide has the formula Fe2O3 and contains Fe3+ ions.
In Fe2O3 + 3CO → 2Fe + 3CO2, which substance is reduced?
Fe2O3 is reduced because it loses oxygen to form iron, Fe.
In Fe2O3 + 3CO → 2Fe + 3CO2, which substance is oxidised?
CO is oxidised because it gains oxygen to form CO2.
State what OIL RIG stands for in the context of redox reactions.
OIL RIG is a mnemonic: Oxidation Is Loss (of electrons) and Reduction Is Gain (of electrons). It summarises the electron transfer definitions of oxidation and reduction.
True or False?
In a redox reaction, the species that is oxidised loses electrons and its oxidation number increases.
True.
When a species is oxidised it loses electrons, which causes its oxidation number to increase. For example, Fe loses electrons to become Fe2+, so its oxidation number increases from 0 to +2.
In the reaction Fe + Cu2+ → Fe2+ + Cu, iron is .......... because it .......... electrons, and Cu2+ is .......... because it .......... electrons.
In the reaction Fe + Cu2+ → Fe2+ + Cu, iron is oxidised because it loses electrons, and Cu2+ is reduced because it gains electrons.
What is the role of the oxidising agent in a redox reaction?
The oxidising agent accepts electrons from another species. In doing so, it is itself reduced (its oxidation number decreases).
What is the role of the reducing agent in a redox reaction?
The reducing agent donates electrons to another species. In doing so, it is itself oxidised (its oxidation number increases).
In the half-equation Ag → Ag+ + e-, silver is .......... because it .......... an electron.
In the half-equation Ag → Ag+ + e-, silver is oxidised because it loses an electron.
In the half-equation O2 + 4e- → 2O2-, oxygen is .......... because it .......... electrons.
In the half-equation O2 + 4e- → 2O2-, oxygen is reduced because it gains electrons.
How do you identify which species has been oxidised in the ionic equation V3+ + Fe3+ → V4+ + Fe2+?
V3+ is oxidised because it loses one electron to become V4+, increasing its oxidation number from +3 to +4. Fe3+ is reduced because it gains one electron to become Fe2+.
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