Unit 2-Redox Reactions

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  • Created by: Heather
  • Created on: 28-03-15 15:35
What does the term redox mean?
Reactions which involve both reduction and oxidation and describes reactions in which electrons transferred from one species to another,
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What is the definition of oxidation?
A reaction in which an atom of group of atoms loses electrons,
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Give an example of the oxidation of copper?
Cu(s) + 0.5 O2 = CuO(s)
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What is the oxidising agent in this reaction?
Oxygen,
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What is the definition of an oxidising agent?
Electron acceptors,
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What is the definition of reduction?
A reaction in which an atom or group of atoms gain electrons,
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Give an example of the reduction of Copper oxide with hydrogen?
CuO(s) + H2(g) = Cu(s) + H2O(l)
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What is the reducing agent in the reaction?
Hydrogen
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What is the definition of a reducing agent?
Electron donors,
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What is the oxidation state of elements not combined with others?
0
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What is the oxidation state of oxygen in compounds except peroxide?
-2
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What is the oxidation state of oxygen in peroxides?
-1
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What is the oxidation state of hydrogen in compounds except metal hydrides?
+1
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What is the oxidation state of hydrogen in metal hydrides?
-1
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What is the oxidation state of Group 1 metals in a compound?
+1
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What is the oxidation state of Group 2 metals in a compound?
+2
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What is the oxidation state of phosphorus PO4 with an overall charge of -3?
Oxidation state of oxygen= -2 x 4= -8 Oxidation state of phosphorus-3+8= +5
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Is an element with a -3 charge more likely to be oxidised or reduced?
Oxidised as more likely to lose electrons,
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Is an element with a +3 charge more likely to be oxidised or reduced?
Reduced as more likely to gain electrons,
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What are half equations used for?
One shows reduction, one shows oxidation in an overal redox reaction,
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What two things in a half equation must be balanced?
-Number of atoms, -Number of charge,
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In the equation Fe2O3 + 2Al = Al2O3 + 2Fe, what is oxidised and why?
Aluminium is oxidised from its oxidation state of 0 to +3,
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Give the half equation for the oxidation of aluminium for this reaction
Al-> Al3+ + 3e-
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In the equation Fe2O3 + 2Al = Al2O3 + 2Fe, what is reduced and why?
Iron is reduced from its oxidation state of +3 to 0,
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Give the half equation for the reduction of iron for this reaction?
Fe3+ + 3e- = Fe
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In the equation Cl2 + SO2 + 2H2O = H2SO4 + 2HCl, what is reduced and why?
Chlorine is oxidised from its oxidation state of 0 to -1,
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Give the half equation for the oxidation of chlorine for this reaction?
Cl2 + 2e- -> 2Cl-
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In the equation Cl2 + SO2 + 2H2O = H2SO4 + 2HCl, what is oxidised and why?
Sulfur from its oxidation state of +4 to +6
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Give the half equation for the oxidation of sulfur?
SO2 + 2H20 -> H2SO4 + 2H+ + 2e-
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For half-equations for reactions occuring in aqueous solution, what is 'surplus' oxygen converted into to and how?
-Wate,r -By reaction of oxygen with hydrogen ions from an acid,
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Deduce the half equation for the reduction, in acid solution, of NO3- to NO?
NO3- + 4H+ + 3e- -> NO + 2H20
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For the two half equations: Cl2 + 2e- -> 2Cl- and 2Br- -> Br2 + 2e-, write the overall equation for the redox reaction?
Cl2 + 2Br- -> Br2 + 2Cl-
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If the same species appears on both sides of an overall equation obtained in two half equatiions, what is it necessary to do?
Cancel out the species so it only on one side of the final equation,
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Card 2

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What is the definition of oxidation?

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A reaction in which an atom of group of atoms loses electrons,

Card 3

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Give an example of the oxidation of copper?

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Card 4

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What is the oxidising agent in this reaction?

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Card 5

Front

What is the definition of an oxidising agent?

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