Hello!
The average reaction rate for this reaction is 0,0038 M/s
The equation for reaction rate in this chemical reaction (for CuCl₂) is the following one (The value 1/3 comes from the coefficient in the chemical equation for the reaction):
[tex]rate= -\frac{1}{3} * \frac{C2-C1}{t2-t1}= -\frac{1}{3} * \frac{0,655M-1M}{30s-0s}=0,0038 M/s[/tex]
Have a nice day!