A chemist studies three separate gaseous equilibria at the same temperature

CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)

Problem

A chemist studies three separate gaseous equilibria at the same temperature. The equilibrium constants are provided in the table below.

Reaction	Equation	$K_c$
I	$\text{A}(g)\,\rightleftharpoons\,2\,\text{B}(g)$	$1.2\times10^{4}$
II	$\text{C}(g)\,\rightleftharpoons\,\text{D}(g)+\text{E}(g)$	$3.5\times10^{-7}$
III	$2\,\text{F}(g)\,\rightleftharpoons\,\text{G}(g)$	$6.0\times10^{1}$

(1) Rank the three reactions in order of increasing fraction of products present at equilibrium (least product present to most product present). (2) Identify which reaction, if any, can be considered to proceed essentially to completion under these conditions. Justify your choice. (3) For Reaction II, explain how the magnitude of

K_c

reflects the position of equilibrium in terms of the relative moles of

\text{C}

versus the combined moles of

\text{D}

and

\text{E}

. Include an explanation of why the stoichiometry matters when interpreting

K_c

Related theory

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