kinetics summary

Question

F and G react together. When the concentration of F is tripled and the concentration of G remains constant, there is a nine-fold increase in the rate of the reaction. What is the order of the reaction with respect to F?

Answer 1

Hi Margie!

When we say "reaction order," we're referring to the value of the exponent on a reactant's concentration in the rate equation. In the same way that we say the "order" of a quadratic polynomial is 2, or a cubic polynomial is 3, because that is the value of their largest respective exponents, we say that the order of a reaction with respect to a reactant is the exponent that is applied to that reactant in the rate equation.

So what we have here is some equation like this:

rate = k[F]^m[G]ⁿ

The order of the entire reaction would be m+n; however, we are being specifically asked for the reaction rate with respect to F (This tells us how quickly the rate of the equation increases as the concentration of F increases).

Since a 3-fold increase in the concentration of F yields a 9-fold increase in the rate, we can find that the exponent m necessary to allow this is 2, since 3²=9.

So, if you doubled F instead of tripling it, you would have gotten a 4-fold increase. If you had quadrupled it instead of tripling it, you would have gotten a 16-fold increase!

I hope this helps! If you'd like more help in this vein, please take a look at my profile and contact me-- I'd be happy to tutor you!