The material, Brass is not an element. The different elements can be seen on the periodic table. Anyway, brass is an alloy of metal. Although, gold, silver, copper and many others are elements. Hope i helped. Have a nice day.
Answer:

27.70 is
for the reaction.
Explanation:

The equilibrium constant of the reaction = 
The expression of equilibrium constant is given by :
..[1]

The equilibrium constant expression for above reaction can be written as:
![K_c'=\frac{[COBr_2]^2}{[CO]^2[Br]^2}](https://tex.z-dn.net/?f=K_c%27%3D%5Cfrac%7B%5BCOBr_2%5D%5E2%7D%7B%5BCO%5D%5E2%5BBr%5D%5E2%7D)
( from [1])

27.70 is
for the reaction.