This is the balanced chemical equation for the reaction between nitric acid (HNO3) and copper (Cu) to produce copper(II) nitrate (Cu(NO3)2), nitrogen dioxide (NO2), and water (H2O):

3HNO3 + 8Cu -> 3Cu(NO3)2 + 2NO2 + 4H2O

The reaction is balanced with 3 moles of nitric acid reacting with 8 moles of copper to produce 3 moles of copper(II) nitrate, 2 moles of nitrogen dioxide, and 4 moles of water.