Redox Reactions?
Answer:
First balance the copper half reaction:
Everything is already balanced so all you have to do is add two electrons to balance the charge
Cu = Cu2+ + 2e-
Then balance the HNO3 half reaction:
HNO3 = NO2
Nitrogen is balanced, so balance the Oxygens by adding water
HNO3 = NO2 +H2O
Then balance the hydrogens by adding H+ ion
H+ + HNO3 = NO2 + H2O
Then balance the charges with electrons
e- + H+ + HNO3 = NO2 + H2O
Then add the two equations together making sure the electrons cancel.
*Note* the second equation must be multiplied by 2 so the electrons will cancel.
2(e- + H+ + HNO3 = NO2 + H2O)
=
2e- + 2H+ + 2HNO3 = 2NO2 + 2H2O
+
Cu = Cu2+ + 2e-
Make sure to cancel out anything else that would end up on both sides. Nothing else is on both sides so the final equation added together is:
Cu + 2H+ +2HNO3 = Cu2+ + 2NO2 + 2H2O
Hope that clears things up.
Cu--------> Cu+2 + 2e- (oxidation)(1 half)
2NO2+ + 2e- -------> 2NO2 (reduction)(2 half)
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