chemistry
posted by Kimberky .
"What effect does doubling (S2O8)^2 have on the rate?" I don't understand that question. Could you please explain it?

You must be talking about kinetics. If the rate is r = k(S2O8^{2}) and it is a first order equation, then doubling the concn will double the rate.
If it is a second order equation, for example,
r = k(S2O8^{2})^{2}, then doubling concn will quadruple the rate. etc.