A specialty chemical plant produces phosgene,

CHEMISTRY · Multi-part · A Level · Chemistry · Energetics · Energetics

Problem

A specialty chemical plant produces phosgene, COCl2(g)\text{COCl}_{2}(g), in two consecutive furnace zones. The overall process is summarized by the target reaction below, but each zone carries out only one of the intermediate reactions. Zone A: 12 O2(g)+C(s,graphite)→CO(g)\dfrac12\,\text{O}_{2}(g)+\text{C}(s,\text{graphite})\rightarrow\text{CO}(g) ΔHA=−110.5 kJ\Delta H_{A}=-110.5\,\text{kJ} Zone B: CO(g)+Cl2(g)→COCl2(g)\text{CO}(g)+\text{Cl}_{2}(g)\rightarrow\text{COCl}_{2}(g) ΔHB=−220.1 kJ\Delta H_{B}=-220.1\,\text{kJ} Target overall reaction: 12 O2(g)+C(s,graphite)+Cl2(g)→COCl2(g)\dfrac12\,\text{O}_{2}(g)+\text{C}(s,\text{graphite})+\text{Cl}_{2}(g)\rightarrow\text{COCl}_{2}(g) The plant must supply phosgene at a rate of 8.00×103 kg day−18.00\times10^{3}\,\text{kg\,day}^{-1}. (a) Confirm algebraically that adding the Zone A and Zone B reactions yields the target overall reaction. State the enthalpy change ΔHtarget\Delta H_{\text{target}} for producing exactly one mole of COCl2(g)\text{COCl}_{2}(g). (b) Phosgene has a molar mass of 98.9 g mol−198.9\,\text{g}\,\text{mol}^{-1}. Calculate the number of moles of phosgene produced per day. (c) Determine the total daily heat released or absorbed by the combined operation of both furnace zones. Report your answer in megajoules (MJ). (d) For safety, the reactor jackets can remove a maximum of 2.0×103 MJ2.0\times10^{3}\,\text{MJ} of heat per day. Assess whether additional cooling capacity is required and justify your answer quantitatively. (e) Suppose process optimization doubles the throughput while keeping both reactions thermally isolated. Explain qualitatively and quantitatively how this change affects the heat management strategy developed in part (d).

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