[Catalist] Equilibrium and temperature

Sat Nov 25 03:44:14 AEDT 2017

Hi again

Agree with you all - and kids should definitely use roy’s suggested
statement in assessments.

But I think Brian is onto the most teachable explanation, so after a bit of
a hunt, found:
They need a bit of streamlining, but they kinda sum up everyone’s
contribution. Arrhenius was the next slide BTW and heat makes an appearance
too :) Nothing about entropy, but I can live with that.

Cheers
Andy

On Fri, 24 Nov 2017 at 3:44 pm, PLEWRIGHT Brian [Broome Senior High School]
<Brian.Plewright at education.wa.edu.au> wrote:

> [image: http://www.ibchem.com/IB/ibfiles/energy/ene_img/boltz1.gif]
>
> A colleague showed me this a few years back when we were chatting at
> Future Science.
>
>
>
> As temp increases the proportion of particles with energy greater than Ea
> increases and reaction rate increases. So both forward and reverse rates
> increase.
>
> However, if you look at the above diagram, if the Ea on the above diagram
> represented the higher Ea or the endothermic reaction in the equilibrium
> situation this thread is talking about, you could estimate that the rate of
> the endothermic reaction would be much greater at T2 because the area under
> the curve at T2 is probably 5 times larger (yellow plus orange) than it is
> at T1 (orange only).
>
> If you took the Exothermic reaction to have a very low Ea (which is not
> labelled on this diagram), but let’s say it was the first mark on the Ek
> scale  then the area under the curve at T1 would account for 90% of
> particles and at T2 probably 95% - so the exothermic rate would be faster,
> but only by 1 and a bit, certainly not 5 times the increase as occurred for
> the endothermic reaction. You can try this exercise putting the exo Ea
> closer to the higher endo Ea and the same thing happens – a bigger increase
> in rate for the endothermic (higher Ea) reaction compared to the exothermic
> (lower Ea) reaction.
>
>
>
> [image: BSHS_Logo_JPG]
>
>
>
>
>
> *Dr Brian Plewright HOLA Science*
>
>
>
> T: 08 9195 3100
> E: brian.plewright at education.wa.edu.au
>
> www.broomeshs.wa.edu.au
>
>
>
> *We acknowledge the Djugun Yawuru people, the traditional owners and
> custodians of the land on which we work and learn together. *
>
>
>
>
>
> *From:* Catalist [mailto:catalist-bounces at lists.stawa.net] *On Behalf Of *Andy
> Gray
> *Sent:* Friday, 24 November 2017 2:20 PM
>
>
> *To:* catalist at lists.stawa.net
> *Subject:* Re: [Catalist] Equilibrium and temperature
>
>
>
> Hi Andrew - although outside of the ATAR course,
> http://www.chem1.com/acad/webtext/thermeq/TE5.html
> <https://apac01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.chem1.com%2Facad%2Fwebtext%2Fthermeq%2FTE5.html&data=02%7C01%7CBrian.Plewright%40education.wa.edu.au%7C9c3406a1be384387947008d53303fa34%7Ce08016f9d1fd4cbb83b0b76eb4361627%7C0%7C0%7C636471014561608595&sdata=tGzM7qNhFLqRP6MhV5%2FohDoX4bXeUFbX36%2BkWAuU2Pg%3D&reserved=0>
> is pretty good at explaining the relationship between changes in Gibbs free
> energy and K. Also, https://aatishb.com/entropy/
> <https://apac01.safelinks.protection.outlook.com/?url=https%3A%2F%2Faatishb.com%2Fentropy%2F&data=02%7C01%7CBrian.Plewright%40education.wa.edu.au%7C9c3406a1be384387947008d53303fa34%7Ce08016f9d1fd4cbb83b0b76eb4361627%7C0%7C0%7C636471014561608595&sdata=DoOETuiFwwziN6IrYWbCo8%2FiBiPI9bYviKPuvdnAGoU%3D&reserved=0>
> uses sheep to explain entropy and it's AWESOME!
>
>
>
> Enjoy the weekend :)
>
>
>
> On 24 November 2017 at 12:11, Andrew Bland <abl at gmas.wa.edu.au> wrote:
>
> Dear chemistry teachers,
>
>
>
> When a system is heated, both the forward and reverse reaction rates
> increase, “but the endothermic reaction increases more than the exothermic
> reaction. The endothermic reaction is always affected more by a temperature
> change than the exothermic reaction. This is true even when a system is
> cooled…” Chem for WA 2.
>
>
>
> My question is why is the endothermic reaction rate always effected more
> than the exothermic rate? I cannot find an explanation in any of my texts,
> only a re-stating of this in various forms.
>
>
>
> Thanks
>
>
>
> Andrew
>
>
>
>
>
> Andrew Bland
>
> Head of Year 10 and Head of Geographe House
>
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