The reaction A (l) R(g) is allowed to reach equilibrium conditions in an autoclave. At equilibrium, there are two phases, one a pure liquid phase of A and the other a vapor phase of A, R and S. Initially A alone is present. The number of degrees of freedom are

A. 1

B. 2

C. 3

D. 0

Answer: Option B

Solution(By Examveda Team)

$$f = C - \phi + 2 + {\text{ number of chemical reactions}} + {\text{ number of constraints}}$$
$$ \Rightarrow {\text{ given number of components}} = 3$$
Number of phase $$=2,$$  number of independent chemical reactions $$=1,$$  number of constraints $$= 1$$  (initially only $$A$$ is present)
So, $$f=2$$