Hi,
I didnt think you wanted the answer straight out, i thought you wanted
to figure it out yourself too.
As someone said, the gain is always 1 (simplest possible) but the
phase varies from 180 to 0 degrees.
Given:
a=1/(R*C)
The transfer function (given already by Roff i think) is:
Vo(s)=Vi*(s-a)/(s+a)
so of course with w=lower case omega=ω,
Vo(jw)=Vi*(jw-a)/(jw+a)
and also of interest is the time domain step response:
Vo(t)=Vi*(2*e^(-a*t)-1)
Note the '2' in the above Vo(t) response, which makes it interesting.