AP Chem - Lab due Monday - Kinetics April 27, 2008

So Torie commented on another post but I thought this deserved its own post.  Here is what she said:

I am confused on the lab with the Mg and HCl.
I got all of the calculations except for the ln [H3O]+. I dont know how to figure that out…

and then the part after that… ln rate= m ln[H3O+] + ln k

I am not sure what to do with that…

[H3O+] is the concentration of H+ or H3O+(same as H+ except it has water attached) in solution.  Since HCl is a monoprotic strong acid, when placed in water, HCl ionizes into H+ and Cl-.  If you have 0.25M HCl, the concentration of H+ in solution will be 0.25M because there is a one to one mole ratio.  So, when they ask for ln[H+], just calculate the natural log of the concentration of your acid.  Since slope-intercept form is y=mx+b, if you plot natural log of rate on the y axis and ln of concentration on the x axis, your y intercept will be the natural log of the rate constant.  This is useful if you want to find out what your rate constant is.  YOu can get the point-slope equation by adding a trendline to your data in Excel and in the extra options, show the equation.  See me in the morning if you still have a question.