Use the information below to determine whether or not a reaction mixture in which the partial pressures of $PCl_3$, $Cl_2$, and $PCl_5$ are 0.21 atm, 0.41 atm, and 0.49 atm, respectively, is at equilibrium at 450 K. $K_p$ = 3.8 at 450 K.
$PCl_3(g) + Cl_2(g) \rightleftharpoons PCl_5(g)$