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posted by  nfekted on 7/23/2008 12:20:31 AM  |  status: Live  

Identifying Redox Reactions

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2Mg(s) + O2(g) -> 2 MgO(s)

2HBr(aq) + Ca(OH)2(aq) -> 2 H2O(l) + CaBr2(aq)

Zn(s) + (aq) -> (aq) + Fe(s)

it also asks for the balanced half reactions
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posted by Ricky Wilkins on 7/23/2008 2:39:10 AM  |  status: Live
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Response Details:
 a) The given reaction is
    2Mg(s) + O2(g) -> 2 MgO(s)
 In this reaction the Oxidation state of the Mg changed from the 0 to +2(Oxidation),while the oxidation state of the Oxygen was changed from 0 to -2(Reduction)
 Therefore  the given reaction is a redox reaction.
 Oxidation : 2Mg(s) ---------> 2Mg+2(aq) + 4e-
 Reduction: O2 (g) + 4e ---------> 2O-2 (aq)

 b)  The given reaction is 
    2HBr(aq) + Ca(OH)2(aq) -> 2 H2O(l) + CaBr2(aq)
 In this reaction there is no chage in the oxidation state of the any element,Hence it is not a redox reaction.

 c)Zn(s) + (aq) -> (aq) + Fe(s)
  In this reaction the Oxidation state of the Zn changed from the 0 to +2(Oxidation),while the oxidation state of the Fe+2 was changed from +2 to 0(Reduction)
 Therefore  the given reaction is a redox reaction.
 Oxidation : Zn(s) ---------> Zn+2(aq) + 2e-
 Reduction:  Fe+2(aq) + 2e --------->  Fe (aq)

 
 
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