Which of the following best explains why pure liquids are excluded from…
CHEMISTRY · Single correct · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
Which of the following best explains why pure liquids are excluded from equilibrium-constant expressions?
(a) Their concentration is effectively zero in the reaction quotient, so including them would not affect K.
(b) Because the number of moles of a pure liquid does not change during the reaction, it is left out of the expression for K.
(c) Pure liquids have an activity of 0 since ln0 in the definition of chemical potential would otherwise be undefined, so they are excluded.
(d) Their molar concentration is effectively constant because it depends only on the substance’s density, not on the amount present.