Writing Rate Laws

[Bronson Mathos 1H]

Hello, I was wondering if someone could explain to me how to go about writing rate laws for when k is the rate constant, as I struggled on that part of the question on question 7 on week 9 and 10 of Sapling?

[Sydney Lam_2I]

Hi! So it really depends on what information is given to you! If they give you the table you want to cancel out the concentrations until there is only 1 left with an unknown exponent and continue solving until you have all of them. For elementary steps you would just use the stoich coefficients and get rid of any intermediates.

[Scot Widjaja Dis 1J]

In general, when we are given experimental data, we write rate laws in the form rate = k(reactant 1)^n * (reactant 2)^m and so on for all the reactants. To find the order with respect to each reactant (defined my n and m in the above equation) we need to analyze the experimental data. Assume there are only two reactants. we have to find out what happens to the rate of reaction when one concentration of reactant doubles (by doing this, we need to keep the concentration of the other reactant constant). If we a double a concentration and the rate doesn't change, then the order is 0 with respect to the reactant. If we a double a concentration and the rate also doubles (multiplies by the same amount), then the order is 1 with respect to the reactant. If we a double a concentration and the rate quadruples (multiplies by 4), then the order is 2 with respect to the reactant.