Gen chem question on Bootcamp and Destroyer

[teefdocta]

Destroyer 2014, gen chem #164 suggest that a collision will less likely to occur when there is too many reactant. But increasing the reactant concentration will increase the frequency of collision, isn't it?

Also on bootcamp #2

14. N2(g) + 3H2(g) ⇌ 2NH3(g) ; ΔH° = -92.22 kJ•mol-1

Which change would decrease the Keq in the above reaction?

• A. Adding an iron catalyst.
• B. Decreasing the volume of the vessel.
• C. Injecting H2 gas.
• D. Cooling ammonia gas into a liquid.
• E. Increasing the temperature.

I got E correct but in the explanation, it states "Lastly, cooling ammonia gas into liquid will pull the reaction towards the right to produce more products, increasing Q." Would cooling down also consider to be decrease in temperature, and the principle of reducing heat in an exothermic reaction would drive the reaction to the right and thus increase K (not Q)?

Someone enlighten me please . And thank you for the inputs.

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[ThunderSplash]

For the first one, imagine you and a few friends are throwing marbles. Pretend that when marbles collide, they react (like a chemical reaction). Now imagine one of your reactions was able to proceed when just two marbles collided. It would look something like A + B --> C + D. (Where A and B are the marbles). It wouldn't be hard for you and another friend to throw one marble each and make them collide, thus completing the reaction.

Now imagine you have a reaction like 2A + 2B ---> C + 3D. This means you need 4 reactants (2 "A" marbles and 2 "B" marbles) to collide at the same exact time. Now think of how hard it would be for you and three friends to all throw a marble and make them all four collide at the same exact time. Doing that would be way harder than just colliding two marbles. I hope that makes more sense now!

 

[teefdocta]

For the first one, imagine you and a few friends are throwing marbles. Pretend that when marbles collide, they react (like a chemical reaction). Now imagine one of your reactions was able to proceed when just two marbles collided. It would look something like A + B --> C + D. It wouldn't be hard for you and another friend to throw one marble each and make them collide, thus completing the reaction.

Now imagine you have a reaction like 2A + 2B ---> C + 3D. This means you need 4 reactants (marbles) to collide at the same exact time. Now think of how hard it would be for you and three friends to all throw a marble and make them all four collide at the same exact time. Doing that would be way harder than just colliding two marbles. I hope that makes more sense now!

Thank you, so it's really not the concentration of the reactant but the "pieces" that actually take part in reaction that make it easier to collide. I see it now.

 

[ThunderSplash]

Yes! Sure if the concentrations were super high or something you could take that into account, but generally the more molecules that need to react at the same time, the slower the reaction is. I forgot to quote you. Sorry.

 

[teefdocta]

It's ok! My DAT is on Monday and I'm super nervous (. This is the most painful and tortured ever

 

[ThunderSplash]

It's ok! My DAT is on Monday and I'm super nervous (. This is the most painful and tortured ever

Just recap on weaknesses and take some time the day before the test to relax! I think you'll surprise yourself in a good way. It seems most people do. Good luck friend!