Question

Which of the following statements is/are not true for the reaction between MnO^-4 and S^2–?

• (A) 1 millimole of S^2– is equivalent to 0.4 millimoles of MnO^-4 .
• (B) 1 millimole of MnO^-4 is equivalent to 5 millimoles of S^2–.
• (C) 1 millimole of MnO^-4 produces 2.5 millimoles of S.
• (D) Mn²⁺ and S are produced in the mole ratio 2 : 5.

Answer 1

The Correct Option is B

Explanation:
Balanced half reactions are:${\mathrm{MnO}}_4^{-}+8{\mathrm{H}}^{+}+5\mathrm{e}\to {\mathrm{Mn}}^{2+}+4{\mathrm{H}}_2\mathrm{O}$$s^{2-}\to s+2e$So, the balanced equation is:$2{\mathrm{MnO}}_4^{-}+16{\mathrm{H}}^{+}+5.{\mathrm{s}}^{2-}\to 2{\mathrm{Mn}}^{2+}+8{\mathrm{H}}_2\mathrm{O}+5\mathrm{s}$1 millimole of $s^{2-}$ is equivalent to $2/5=0.4$ millimoles of $Mn{O}_4^{-}$ 1 millimole of $Mn{O}_4^{-}$ produces $5/2=2.5$ millimoles of $S$${\mathrm{Mn}}^{2+}$ and $\mathrm{S}$ are produced in the ratio 2: 5 Hence, the statements (1),(3) and (4) are correct.