1 mole each of A and B are mixed initially  in one lit closed flask at room temperature. If the equilibrium constant for the reaction A$\rightleftharpoons$B is 0.5. Identify the correct statement from the following at equilibrium state?

all reaction components are present initially, initial reaction quotient is

${\mathrm{Q}}_{\mathrm{c}}=\frac{{\displaystyle \frac{1}{2}}}{{\displaystyle \frac{1}{2}}}=$1

Q_c > K_c equilibrium moves from right to left ( products to reactants)

$\underset{+\mathrm{x}}{\overset{1 \mathrm{mole}}{\mathrm{A}}}\rightleftharpoons \underset{-\mathrm{x}}{\overset{1 \mathrm{mole}}{\mathrm{B}}}$

at equilibrium 

[A] = 1+x and [B] = 1-x

K_c = $\frac{\left[\mathrm{A}\right]}{\left[\mathrm{B}\right]}$ = 2(equilibrium is reversed its equlibrium constant is reciprocal)

$\frac{1+\mathrm{x}}{1-\mathrm{X}}=2$

x =$\frac{1}{3}$

[A] = $1+\frac{1}{3}=\frac{4}{3}$

[B] = $1-\frac{1}{3}=\frac{2}{3}$