Please balance the following equation at 25 degrees C by writing the correct coe
ID: 732241 • Letter: P
Question
Please balance the following equation at 25 degrees C by writing the correct coefficients in the spaces provided...__Al(s) + __Cu2+(aq)---> ___Al3+(aq) + ___Cu(s)
Explanation / Answer
From LEO GER (or OIL RIG), Losing electrons oxidation, Gaining electrons reduction. To make your half reactions, prepare the reactions individually, such that all elements are grouped into each half reaction. Two elements occur: Al and Cu, these will be your two half reactions: one for Al and one for Cu Al(s) --> Al3+(aq) and Cu2+(aq) --> Cu(s) Now, there is something missing in these half reactions... ELECTRONS (for the charges must be balanced on both sides... in the Al reaction, we have 0 charge on one end and 3+ on the other, for Cu reaction we have 2+ on one end and 0 on the other). As such: Al(s) --> Al3+(aq) + 3e-(aq) Cu2+(aq) + 2e-(aq) --> Cu(s) From this, and LEO GER, you can see Cu is reducing, and Al is oxidizing. These are your half reactions! Now, to bring them together, we must get the electrons on both sides to cancel out. Notice how we have electrons on one side for one reaction, and the other side for the other reaction? This is good... this will allow us to "cancel" out the electrons when we combine these equations. If you don't get this when working it out, it means you have two incompatible half reactions, and you might want to double check your work. Anyway, to cancel the electrons on both sides, you need to be able to get them to the same quantity. This can be done by multiplying the entire Al oxidation reaction by 2 and the Cu reduction reaction by 3, which results in: 2Al(s) -----> 2Al3+(aq) + 6e-(aq) 3Cu2+(aq) + 6e-(aq) ------> 3Cu(s) --------------------------------------… 2Al(s) + 3Cu2+(aq) ------> 2Al3+(aq) + 3Cu(s) Look at how beautifully the electrons cancel out on both sides. This leaves use with a BALANCED equation for the cell. Now, double check: See if you have each element in the correct proportion and see if your equation is balanced for charge. On both sides, we have 2 Al atoms and 3 Cu atoms. In addition, both sides have 6+ net charges. We have balanced it correctly! Awesome!