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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: TheDangerBone on September 16, 2014, 09:05:06 PM

Title: Help with an equilibrium problem
Post by: TheDangerBone on September 16, 2014, 09:05:06 PM
C (s) + CO2 (g)  ::equil:: 2 CO (g)

ΔH for the rxn above is greater than zero. Assume ΔH is independent of temperature, which of the following is true about the % yield of CO (g)

(a) It increases as the amount of C(s) increases.
(b) It increases as the temperature increases.
(c) It decreases as the temperature increases.
(d) It doubles when the initial partial pressure of CO2 is doubled.
(e) It increases when the total pressure of the reaction system increases.

So I think I understand why (b) is the correct answer, as you increase temperature the -TΔS term increases giving a more negative ΔG. But why is (a) not the correct answer. According to Le'Chatelier's Principle shouldn't adding more C (s) shift the rxn to the right?
Title: Re: Help with an equilibrium problem
Post by: Borek on September 17, 2014, 02:49:23 AM
C is a solid, what do you know about solids and equilibrium? Write equation for equilibrium constant.
Title: Re: Help with an equilibrium problem
Post by: TheDangerBone on September 17, 2014, 11:24:28 AM
Quote from: Borek on September 17, 2014, 02:49:23 AM
C is a solid, what do you know about solids and equilibrium? Write equation for equilibrium constant.

Ahhh...
Pure solids and liquids have an activity of 1 at equilibrium. Nice.
K=[CO]2/[CO2]

Thank you Borek!!!