Hi,
There seems to be some missing info.
First off,
The impedance of the circuit is (note that "w" and "c" are both in the denominator):
Z = R -J(1/w*c)
Don't forget, the impedance of the capacitor is not 1/w*c it is 1/J*w*C, where J is sqrt(-1). It is inconvenient to work with "J" in the denominator so if you multiply the numerator and the denominator by J/J (i.e. 1) then the result is: -J(1/w*c)
The magnitude of the impedance is:
|Z| = sqrt[R^2 + (1/w*c)^2]
For very low frequency, the impedance of the capacitor is very large
For very high frequency, the impedance of the capacitor is very small
So I would expect the magnitude of the impedance to have a constant negative slope (i.e. a line with negative slope) that extends from low frequency and approaches the value of "R" as frequency increases. This assumes that you plot magnitude of Z against "w" on a log-log plot.
So the plot looks like:
Hope this helps.
Regards,
Frank