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5I.13

Posted: Sun Jan 12, 2020 9:41 pm
by Jeremy_Guiman2E
5I.13

(a) In an experiment, 2.0 mmol Cl2(g) was sealed into a reaction vessel of volume 2.0 L and heated to 1000. K to study its dissociation into Cl atoms. Use the information in Table 5G.2 to calculate the equilibrium composition of the mixture.
(b) If 2.0 mmol F2 was placed into the reaction vessel instead of the chlorine, what would be its equilibrium composition at 1000. K?
(c) Use your results from parts (a) and (b) to determine which is thermodynamically more stable relative to its atoms at 1000. K, Cl2 or F2.

Hi, could someone explain how to go about this problem step by step? Thanks.

Re: 5I.13

Posted: Mon Jan 13, 2020 2:12 pm
by GFolk_1D
Hi this is a pretty involved question and I was confused at first as well but the step by step solution in the Solutions Manual was really helpful!

Re: 5I.13

Posted: Mon Jan 13, 2020 2:27 pm
by Brian Tangsombatvisit 1C
a) convert Cl2 to mol/L (for concentration) first. Then, set up your ice table (start with 0.0010 M Cl2 and 0 M Cl). You don't know how much of Cl2 was used up, so you represent the change as -x. Plug in the expressions at equilibrium into the expression for K, which is in terms of x. Use algebra to rearrange the equation into quadratic form, so you can use the quadratic formula to solve for x. Choose the positive value of x and plug it back into the ice table. Since the x value is so small compared to the original starting amount of Cl2, we can say that virtually no Cl2 was converted to 2Cl. You can find the final conc of Cl by plugging x into the 2nd column of the ice table.

b) this is the same process as part a) except the new given equilibrium constant for this particular reaction at this particular temp is 1.2x10^-4 instead of 1.2x10^-7.

c) Cl2 is more stable since it has a smaller equilibrium constant than F2, meaning that less of it dissociates into its singular atom form than F2. This is also supported by the fact that less product is formed in the reaction with Cl2 than F2. If a molecule is more stable, it will not dissociate as much.

Re: 5I.13

Posted: Mon Jan 13, 2020 5:47 pm
by Jeremy_Guiman2E
Thank you Brian, this was really helpful!