[meshohel]

reaction like
A+B+C--->D+E+F

If I change only the concentration of C (five different concentrations) keeping concentration of A and B constant, the plot of {concentration of A vs time} will give different initial rates. My detection system will allow me to detect A only at different time.
Now from conc. vs time curve, I can get rate of reaction and as well as concentration of A at different times.
The plot of log rate against log conc. will show up a straight line. The slope will give us the order with respect to reactant C and the intercept will give us the value of rate constant.

The above statement is true or not???

Now since rate constant and orders are constant for a reaction, these two values must be constant at different concentration of reactant C.
In my experiments I found these two values changes at different concentrations of starting materials. Also the plot of log rate vs log concentration becomes nonlinear (curve).

What could be the reason for this???
I need your help.

For example
[A]         [C]                                               Temp.      Initial rate            rate constant     Order
0.1   0.1   0.1         25   2.27E-04      0.238            3.01823
0.1   0.2   0.1         25   5.94E-04      660.29            6.0387
0.1   0.3   0.1         25   7.82E-04      9.88E-04            0.10158
0.1   0.4   0.1         25   1.49E-03      0.0628            1.6162
0.1   0.5   0.1         25   4.52E-03      61.31            3.98585