Final answer:
The mass of reactants used during the reaction hydrogen bromine = hydrogen bromide is not provided in the given information. We only have the concentration of bromine gas at equilibrium.
Step-by-step explanation:
The reaction is:
H₂ + Br₂ → 2HBr
Since the reaction begins with only HBr and the mole ratio of H₂ to Br₂ is 1:1, the concentration of H₂ at equilibrium is also 0.00243 M. The equilibrium expression can be rearranged to solve for the concentration of HBr at equilibrium.
Therefore, the mass of the reactants used during the reaction is not provided in the given information. We only have the concentration of bromine gas at equilibrium.