When copper metal is added to nitric acid, the following reaction takes place cu (s) + 4 hno₃ (aq) → cu(no₃)₂ (aq) + 2 h₂o (l) + 2 no₂ (g) calculate the volume in liters of no₂ gas collected over water at 25. 0 °c when 2. 01 g of copper is added to excess nitric acid if the total pressure is 726. 0 mmhg. The vapor pressure of water at 25. 0 °c is 23. 8 mm hg.