Equilibrium constant question (1 Viewer)

[rockstar01]

Many industrial chemical processes involve equilibrium reaction. For example, the gas carbon oxyfluoride (COF2) decomposes to the gas carbon tetrafluoride (CF4) and carbon dioxide.

(i) Write a balanced equation for the reaction, and hence write the expression for the equilibrium constant for this reaction.

The reaction is carried out at 200*C in a fixed-volume 10 litre container. Initially, there are 2.0 moles of carbon oxyfluoride gas in the flask. At equilibrium, 80% of the carbon oxyfluoride has decomposed.

(ii) Determine the value of the equilibrium constant.

(iii) The enthalpy change for the decomposition of carbon oxyfluoride is -24 kJ mol. Explain the effect of an increase in temperature on the equilibrium constant.



I can do i and iii but I'm having a bit of trouble with ii....any help?

 

[mitochondria]

i) 2COF₂ -------> CF₄ + CO₂

ii) 2COF₂ -------> CF₄ + CO₂

Using ICE:
I ------ 0.2, 0, 0
C ----- -0.16, +0.8, +0.8
E ----- 0.04, 0.8, 0.8

(Clearly, you work out the concentrations by dividing the amount of substances in moles by the volume...)

The equilibrium constant K, for this reaction is:

K = [CO₂][CF₄] / [COF₂]² = 0.8² / 0.04² = 400

iii) ∆H_decomp = -24 ----> Therefore the reaction is exothermic. If you increase the temperature the system will seek to minimise the disturbance by reducting the temperature, i.e. the equilibrium shifts to the left because the reverse reaction is endothermic.

Hope that helps Good luck!

 

[rockstar01]

Thanks

so simple!

 

[sicarphime]

OOPSi got the units wrong and i didnt see the above slutions cos i was on a different mode!

yea! i tried =)

 

[xx06]

I don't get the 'ICE' bit.

 

[priesty]

The ICE bit is simply "Intial. Change. Equilibrium" So u look at the original starting concentrations. Then put in the change to whatever the question says and balance it out onto the other compounds. Then recalculate the equilibrium after those changes using PORK Simple

They usually call it the ICE CUBE. Coz u can draw it up into a table... hehe

PORK - Products Over Reactants = K - i loved that one.