[INeedSerotonin]

The reaction between persulfate and iodide, at 25°C, is given as

S₂O₈^-- + 3 I^- --> 2 SO₄^-- + I₃^-

and it shows a velocity, determined experimentally, as

v = k. [S₂O₈^--] . [i^-]

Assign "true" or "false" to the following propositions:

I) This is an oxirreduction reaction;
II) This is a second-order reaction;
III) the reaction rate is directly proportional to the concentration of the reagents;
IV) the rate of disappearance of  [S₂O₈^--] is three times greater than the rate of disappearance of I^-

Which one of these are correct?

Answer: I, II, and III

I don't understand. How come (IV) is not true? Isn't the rate of disappearance inversely proportional to the coefficients?

[AWK]

Maybe the inverted statement is correct.

[mjc123]

What do you think the coefficients mean? 3 I^- are consumed for every S₂O₈^2-.

You may be getting confused with
rate of reaction = 1/a*d[A]/dt
but that is because
d[A]/dt = a* reaction rate

[INeedSerotonin]

Thank you both for helping me. I was indeed getting confused by the algebra.