Lots of problems with the HW you handed in on the method of initial rates (Self test 21.4)

1. In general, make sure you make a table of the numbers you are going to graph. Make sure you do this for the HW for Wednesday as well.

2. On this assignment there was confusion about graphing using log or ln. You can use either but several of you mixed when you were trying to use the y- intercept.

3. For this assignment you had to graph using the entire number with common units in order to get the correct y-intercept. For the slope you can use any units because with a ln/ln plot (or log/log) the units cancel out on the slope. (Think back to the heat of vaporization lab.) For example, on the first point you must graph the ln or log of 5.0E-3 moles/l and the ln or log of 3.6E-7 mole/l-s.

4. Don't use one data point with the slope that you found and solve for the specific rate constant. This does not give you the most accurate value. You want to get the best value from all the data for the specific rate constant. Make sure you give the proper units of "k".

5. Make sure you explain using an equation why you are taking "e" to some power or "10" to some power to get "k".

Make sure you have 3 graphs with the associated R^2 values for Prob. 21.1 to prove the order and calculate the rate constant from the slope. Then use the determined rate law to get the mass of cyanate left after 300. min. Make sure you graph the amount of cyanate and not the amount of urea at each instant of time.

We have a lot of graphical analysis as well as regular equations and derivations these last few days together. Finish strong - no regrets!