Question

1) Balance the reaction Fe2+ + MnO4– → Fe3+ + Mn2+ in acidic solution. What is the correct coefficient for Fe2+ when the smallest whole number coefficients are used?

2) Balance the reaction Fe2+ + H2O2 → Fe3+ + H2O in acidic solution. How many electrons are exchanged when the smallest whole number coefficients are used?

3) Balance the reaction Cu + HNO3 → Cu2+ + NO in acidic solution. What is the correct coefficient for NO when the smallest whole number coefficients are used?

4) Balance the reaction CN– + MnO4– → CNO– + MnO2 in basic solution. What is the coefficient of the H2O molecule if smallest whole number ratios are used?

5) Balance the reaction Br2 → BrO3– + Br– in acidic solution. How many moles of electrons are produced if 5 g of Br2 react?

Answer 1

1)

Step-1: split the whole equation into oxidation half and reduction half, observing their change in oxidation states.

Step-2: balance the atoms and molecules on each side of both of the half cell except for oxygen and hydrogen.

Step-3: the side deficient in hydrogen should be balanced by adding h required number of H⁺ ion

Step-4: the side deficient in oxygen should be balanced by adding required number of water molecule and the opposite side should be added with double the number of H ⁺ ion.

Step-5: now balance the charges in both half-cells by adding or subtracting required number of electrons.

Step-6: Finally add both half-cells such that electrons cancels out each other and a balanced equation results.