Copper reacts with nitric acid . A brown gas is formed and the solution turns blue. The equation may be written as : Cu+NO_3^(-) rarr NO_2+Cu^(2+) Balance the equation by oxidation number method.

Copper reacts with nitric acid . A brown gas is formed and the solutio

1.	Copper reacts with nitric acid . A brown gas is formed and the solution turns blue. The equation may be written as : Cu+NO_3^(-) rarr NO_2+Cu^(2+) Balance the equation by oxidation number method.
Answer» Solution :Step 1 : Skeleton EQUATION `Cu+NO_3^(-) rarr NO_2+Cu^(2+)` Step 2 : Writing oxidation numbers of each atom `overset(0)(Cu)+overset(+5-2)(NO_3^(-))rarroverset(+4-2)(NO_2)+overset(+2)(Cu^(2+))` Step 3. The oxidation number copper has increased from 0 to 2 while that of nitrogen has decreased from +5 to +4. Step 4 . Show the increases / DECREASE of oxidation number O.N. increases by 2 per atom Step 5 : Balance the increased /decrease in oxidation number by multiplying `NO_3^(-)` by 2 and Cu by 1. `Cu+2NO_3^(-) rarr NO_2+Cu^(2+)` Step 6. Balance other atoms except H and O as `Cu+2NO_3^(-) rarr 2NO_2+Cu^(2+)` Step 7. Reaction TAKES place in acidic medium , so add `H^+` ions to the side deficient in `H^+` and blance H and O atoms : `Cu+2NO_3^(-) +4H^(+) rarr 2NO_2+Cu^(2+) + 2H_2O`