In this redox reaction, the Cu goes from oxidation state of (0) to (+2), therefore it oxidises. N in HNO₃ goes from oxidation state of (+5) to N in NO with oxidation state of (+2) and becomes reduced. Cu acts as the reducing reagent and HNO₃ is the oxidising agent. oxidation half reaction Cu ---> Cu²⁺ + 2e --1) reduction half reaction 4H⁺ + 3e + NO₃⁻ ---> NO + 2H₂O --2) to balance the number of electrons , 1) x3 and 2) x2 3Cu ---> 3Cu²⁺ + 6e 8H⁺ + 6e + 2NO₃⁻ ---> 2NO + 4H₂O add the 2 equations 3Cu + 8H⁺ + 2NO₃⁻ ---> 3Cu²⁺ + 2NO + 4H₂O add 6 nitrate ions to both sides to add up to 8 and form acid with 8H⁺ ions 3Cu + 8HNO₃ ---> 3Cu(NO₃)₂ + 2NO + 4H₂O Balanced equation for the redox reaction is as follows; 3Cu(s) + 8HNO₃(aq) → 3Cu(NO₃)₂(aq) + 2NO(g) + 4H₂O<span>(l)
