Balance this equation:

Cu + H+(aq) + NO3-(aq) -- Cu2+(aq) + NO2 + H2O

To balance the equation:

Cu + H+(aq) + NO3-(aq) → Cu2+(aq) + NO2 + H2O

The equation appears to be unbalanced as the number of atoms on both sides of the equation does not match.

The first step is to balance the atoms separately. Let's start with the Cu atoms.

On the left side, there is 1 Cu atom, while on the right side, there is 1 Cu2+ atom. To make the Cu atoms balance, you need to add a coefficient of 2 in front of Cu on the left side:

2Cu + H+(aq) + NO3-(aq) → Cu2+(aq) + NO2 + H2O

Next, let's balance the H atoms. On the left side, there is 1 H atom from H+(aq), and on the right side, there are 2 H atoms from H2O. To make the H atoms balance, you need to add a coefficient of 2 in front of H2O on the right side:

2Cu + H+(aq) + NO3-(aq) → Cu2+(aq) + NO2 + 2H2O

Now, let's balance the O atoms. On the left side, there are 3 O atoms from NO3-(aq), and on the right side, there are 1 O atom from NO2 and 4 O atoms from 2H2O. To make the O atoms balance, you need to add a coefficient of 3 in front of NO2 on the right side:

2Cu + H+(aq) + 3NO3-(aq) → Cu2+(aq) + 3NO2 + 2H2O

Finally, let's check if all the atoms are balanced:

Cu: 2 on both sides
H: 3 on both sides
O: 9 on both sides
N: 3 on both sides

All the atoms are now balanced, and the balanced equation is:

2Cu + H+(aq) + 3NO3-(aq) → Cu2+(aq) + 3NO2 + 2H2O