Q.14. For the reaction, 3 \mathrm{I}+\mathrm{S}_2 \mathrm{O}_8^{2-} \rightarrow \mathrm{I}_3^{-}+2 \mathrm{SO}_4^{2-}, at a particular time \mathrm{t}, \frac{\mathrm{d}\left[\mathrm{SO}_4^{2-}\right]}{\mathrm{dt}} is 2.2 \times 10^{-2} \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{~s}^{-1}. What is the value of -\frac{\mathrm{d}\left[\mathrm{I}^{-}\right]}{\mathrm{dt}} ?
A. 1.1 \times 10^{-2} \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{~s}^{-1}
B. 3.3 \times 10^{-2} \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{~s}^{-1}
C. 4.4 \times 10^{-2} \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{~s}^{-1}
D. 6.6 x 10-2 mol dm-3 s-1
Answer:- B. 3.3 \times 10^{-2} \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{~s}^{-1}
Explanation:-
3I+S_{2}O_{8}^{2-}\rightarrow I_{3}^{-}+2SO_{4}^{2-}Rate of reaction = \frac{1}{3}\frac{d[I^{-}]}{dt}=+\frac{1}{2}\frac{d[SO_{4}^{2-}]}{dt}
\frac{d[I^{-}]}{dt}=+\frac{3d[SO_{4}^{2-}]}{2}= \; \frac{3}{2}\times 2.2\times 10^{-2}= 3.3\times 10^{-2}mol \; dm\; s^{-3}