Cu + HNO3 --> Cu(NO3)2 + H2O + NO2 I got an answer of Cu + 2HNO3 --> Cu(NO3)2 + H2O + NO2 My thinking was: on the left there is?

Cu=1 H=2 <-- being multiplied by my inserted coefficient. NO3=2 <--being multiplied by my inserted coefficient. I never touched anything on the right because: Cu=1 NO3=2 <--now equal H=2 <--now equal O=1 NO2=2 I was told to group as many as I could into one substance, that's why I put NO2 as one,... show more Cu=1
H=2 <-- being multiplied by my inserted coefficient.
NO3=2 <--being multiplied by my inserted coefficient.

I never touched anything on the right because:
Cu=1
NO3=2 <--now equal
H=2 <--now equal
O=1
NO2=2

I was told to group as many as I could into one substance, that's why I put NO2 as one, because I did it with NO3. Why is this not the right answer? I was told to group them by one person and told to do them individually by another?
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