JEE Advanced 2014 · Paper 1, Chemistry question 29

Balance. Iodine goes from −1 to 0 (1 e⁻ per I⁻); chlorine goes from +5 to −1 (6 e⁻). So 6 I⁻ per chlorate:
$$\ce{6I- + ClO3- + 6H2SO4 -> Cl- + 3I2 + 6HSO4- + 3H2O}.$$
Charge: $-7$ on the left, $-7$ on the right. O: $3+24=27$ on each side.

• (A) The coefficient of $\ce{HSO4-}$ is 6. True.
• (B) Iodide is oxidised to iodine. True.
• (C) Sulphur stays +6. False.
• (D) Water is a product. True.

(A), (B), (D) (the key accepts A, B, D, or A, D)