Answer : The value of equilibrium constant (Kc) is, 0.0154
Explanation :
The given chemical reaction is:

Initial conc.
0 0
At eqm.
x x
As we are given:
Concentration of
at equilibrium = 
That means,

The expression for equilibrium constant is:
![K_c=\frac{[SO_2][Cl_2]}{[SO_2Cl_2]}](https://tex.z-dn.net/?f=K_c%3D%5Cfrac%7B%5BSO_2%5D%5BCl_2%5D%7D%7B%5BSO_2Cl_2%5D%7D)
Now put all the given values in this expression, we get:



Thus, the value of equilibrium constant (Kc) is, 0.0154
A. The substance dissolved. Just because a substance dissolved in a solvent doesn’t mean that a chemical action occurred. For example, if you put sugar in water as stir, it will dissolve, but the chemical make up of the sugar and the water don’t change. A chemical reaction can be indicated by a drastic change in color or temperature or if a substance precipitate.
Hope this helped :)
Percent composition by mass of oxygen =
((16.0*6)/(40.1+2*(14.0+16.0*3)))*100%
= 58.5%
therefore, the answer is D