Copper refining traditionally involves “roasting” insoluble sulfide ores (CuS) with oxygen. Unfortunately, the process produces large quantities of SO₂(g), which is a major contributor to pollution and acid rain. An alternative process involves treating the sulfide ore with HNO₃(aq), which dissolves the CuS without generating any SO₂. The unbalanced chemical expression for the reaction is given below.

CuS(s)+ NO₃^-(aq) → Cu²⁺(aq) + NO(g) + HSO₄^-(aq)     (not balanced)

What volume of concentrated nitric acid solution is required per kilogram of CuS? Assume that the concentrated nitric acid solution is 70% HNO₃ by mass and has a density of 1.40 g/mL.