A chemical plant is considering a two-step pathway to manufacture ethane (C H )…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A chemical plant is considering a two-step pathway to manufacture ethane (C2H6) starting from calcium carbide (CaC2):
Step 1 CaC2(s) + 2 H2O(l) ⇌ C2H2(g) + Ca(OH)2(s) K1 = 1.6 × 1018 at 298 K
Step 2 C2H2(g) + 2 H2(g) ⇌ C2H6(g) K2 = 1.2 × 102 at 298 K
Assume that each step is carried out separately in its own reactor, starting from stoichiometric reactant mixtures at 1.0 atm total pressure and 298 K, and that the product gas from the first step is fed directly (without purification) into the second reactor along with the required H2.
Answer the following questions.
(a) For each step, classify the reaction as proceeding essentially to completion, reaching an appreciable equilibrium mixture, or showing negligible progress. Support each classification using the numerical values of K1 and K2.
(b) Identify which step is most likely to govern the overall yield of ethane and explain your reasoning.
(c) Propose one practical modification to the reaction conditions of the yield-limiting step that could increase the overall production of ethane, and justify how this modification would affect the position of equilibrium.
(d) Taking your analysis into account, evaluate whether the proposed two-step pathway is suitable for large-scale synthesis of ethane without additional process interventions. Provide a reasoned argument that references your earlier conclusions.