Final answer:
To find the work done against the reaction when 3 moles of H₂ react with 3 moles of Cl₂ to form HCl, the enthalpy change and stoichiometry of the formation must be considered. The calculation suggests that the exothermic reaction releases 276900 J, but the best answer from the provided options is 0 J as none match the calculation and work is typically considered in the context of system expansion, which isn't the focus here.
Step-by-step explanation:
The question involves a chemical reaction between hydrogen (H₂) and chlorine (Cl₂) to form hydrogen chloride (HCl). To calculate the work done against the reaction, we need to consider the enthalpy change, ΔH, of the reaction. Since it's given that 3 moles of H₂ react with 3 moles of Cl₂, this corresponds to 1.5 reactions of the typical stoichiometric reaction H₂ + Cl₂ → 2 HCl in terms of moles, because that reaction involves the formation of 2 moles of HCl.
The enthalpy change for the formation of 2 moles of HCl is -184.6 kJ (given as standard molar enthalpy of formation of HCl(g) = -92.307 kJ/mol). Therefore, for 1.5 times this reaction, the energy given off is 1.5 times -184.6 kJ, which is -276.9 kJ or 276900 J. Since the reaction is exothermic, the work done against the reaction (by the reaction on the surroundings) would be positive 276900 J. However, in the context of the options provided, the best answer would be 0 J, because none of the positive values match our calculation, and typically work is only considered done if it is in the context of the system doing work on the surroundings during expansion, which would not be the main focus in an enthalpy-based question like this one.