posted by Em .
Cu + AgNO3 ---> Ag + Cu(NO3)2 Why is there a two after NO3? Thanks.
The valence of Cu is +2. The valence of the nitrate ion (NO3^-) is -1. For the compound to be zero, the Cu is +2, two nitrates give -2 (at -1 each), +2 and -2 = 0. Thus, one needs two nitrates to equal the charge on one Cu.