Thiosulphate is oxidised to sulphate by chlorine water: S2O3^2- + Cl2 + H2O -> SO4^2- + Cl^- + H^+. Balance with the smallest whole numbers and give the sum of all coefficients (reactants and products) as an integer.

JEE Main levelNumerical answerDifficulty 2 of 3rx069

Thiosulphate is oxidised to sulphate by chlorine water: $S X_{2} O X_{3} X^{2 -} + Cl X_{2} + H X_{2} O SO X_{4} X^{2 -} + Cl X^{-} + H X^{+}$ . Balance with the smallest whole numbers and give the sum of all coefficients (reactants and products) as an integer.

Numerical answer type, tolerance 0.1.

Each S goes from +2 to +6, so

S X_{2} O X_{3} X^{2 -}

loses 8 electrons; each

Cl X_{2}

gains 2, so 4

Cl X_{2}

are needed. Charge and O balance then give

S X_{2} O X_{3} X^{2 -} + 4 Cl X_{2} + 5 H X_{2} O 2 SO X_{4} X^{2 -} + 8 Cl X^{-} + 10 H X^{+}

. The sum of coefficients is 30.