Which equation represents the reduction half-reaction for this redox equation?
Mg + CuSO4 MgSO4 + Cu

A. Cu Cu
B. Cu + 2e- Cu
C. Cu Cu + 2e-
D. Cu + 3e- Cu

Question

Which equation represents the reduction half-reaction for this redox equation?
Mg + CuSO4   MgSO4 + Cu

A. Cu   Cu
B. Cu + 2e-   Cu
C. Cu   Cu + 2e-
D. Cu + 3e-   Cu

anonymous · Answer

@Abhisar

abhisar · Answer

Ok, what do you think it should be? Any Idea?

anonymous · Answer

honestly, not a clue... This is my first time taking chemistry.. & i am LOST.

abhisar · Answer

Fine, do you know what defines a reduction reaction ?

abhisar · Answer

Yes/No?

anonymous · Answer

no.. ? but i can google it. lol

abhisar · Answer

Ok, reduction reaction is when any species gains electron. The reaction which you have been given can be written as follows:-

$\sf Mg + Cu^{+2}+SO4^{-2} \rightarrow  Mg^{+2}+SO4^{-2} + Cu$

abhisar · Answer

Now tell which species on the reactant side has gained electron?

abhisar · Answer

Which one has =+ve charge on the left hand side but is neutral on right hand side?

anonymous · Answer

cu?

abhisar · Answer

Yes, so we can say that the reduction half is :-

$\sf Cu^{2+} +2e^- \rightarrow Cu$

Notice since it had 2+ charge before and neutral after that's why it must have gained 2 electrons.

anonymous · Answer

so the answer is B?

abhisar · Answer

Isn't that obvious ? c:

anonymous · Answer

that's what i chose. thanks!!

abhisar · Answer

You're welcome c: