Half Reactions

  • Thread starter Kaneki123
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  • #1
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I do not have a clear concept about half-reactions...Can someone please give the half reactions for following reaction,
Zn^0 + 2H^1 Cl^-1 -----> Zn^+2 Cl2^-1 + H2^0
or Zn + HCl ----> ZnCl2 + H2
 

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  • #2
HAYAO
Science Advisor
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"Half reaction" is used when you have to deal with oxidation/reduction reactions. Half reaction represents how electron is produced/consumed for reducing and oxidizing agent. So,
Zn = Zn2+ + 2e-
2HCl + 2e- = 2Cl- + H2
Add both equation and you will see.
 
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  • #3
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"Half reaction" is used when you have to deal with oxidation/reduction reactions. Half reaction represents how electron is produced/consumed for reducing and oxidizing agent. So,
Zn = Zn2+ + 2e-
2HCl + 2e- = 2Cl- + H2
Add both equation and you will see.
Also one more thing...In the given equation, the oxidation state of H is changed...So would we say that H is being reduced or its whole compound HCl is being reduced???
 
  • #4
Borek
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In water Cl- is just a spectator, it is H+ that reacts.

But in the gas phase, where only HCl is present I am ready to accept your statement as a correct. Pointing to an element in a compound and stating "this is what is being reduced/oxidized" is often questionable, as it is whole molecule/ion that undergoes the reaction. Yes, when we use oxidation numbers for redox reactions that how we think about the process, but oxidation numbers are just a accounting device designed for keeping track of electrons in the reaction. There is no property of an atom that we can measure to check its oxidation number.
 

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