Textbook Problem

. The equilibrium constant for the reaction
${\text{H}}_{\text{2}}\left(g\right)+{\text{F}}_{\text{2}}\left(g\right)\rightleftharpoons \text{2HF}\left(g\right)$   has the value $2.1\times {10}^3$at a particular temperature. When the system is analyzed at equilibrium at this temperature, the concentrations of both H₂(g) and F₂(g) are found to be 0.0021 M. What is the concentration of HF(g) in the equilibrium system under these conditions?