Possibly yet another stupid chemistry question!
I'm trying to find the activation enthalpy using the annoying (I don't do maths!) Arrhenius equation. Therefore I need the rate constant at my 5 different temperatures. The stupid thing is I changed my method after finding the rate equation and rate constant at 298K. Instead of using the initial rates method I decided I would use the reciprocal (sp?) of time instead, as I only recorded the time taken for my solution to reach 50% transmission on the colorimeter rather than taking a reading every 30seconds for 6mins.
Basically I want to know how to calculate the rate using my new method!
I think it's something like:
rate = concentration of I2 needed for 50% transmission/time taken for 50% transmission to me reached
therefore as concentration of I2 needed will be the same each time;
rate is proportional to 1/time taken
(does proportional mean same as equals?!)
- no: "rate is proportional to 1/time" means rate equals 1/time multiplied by a constantIs this right? What are my units? (concentration is in moldm-3, time is in mins but easily convertable into seconds) Is it moldm-3s-1?
yeah, I think so; yes, the units are mol dm^-3 s^-1 I need the rate to substitue it into my rate equation as follows;
rate = k [propanone] [acid catalyst]
and I need the k for the Arrhenius equation to plot 1/T (T=temp in Kelvin) agains log k! (Don't get me started on logarithms...I know to press 'log' on my calculator but otherwise don't really understand all of that yet!)
- want an explanation? I still find them difficult to get my head round when I'm working with them but the principle is relatively easy I feel silly for asking but I'm not sure & its driving me nuts! Thanks