AQA Chemistry A-Level Paper 1 June 2018 Walk Through (part 1)

Показать описание

Questions 1 to 4 covered

Рекомендации по теме

Комментарии

Great vid however 1.2 is added incorrectly should total to 3888 :)

jailbreaker

9:57
everyone's seeming to skip this point out...
we know that the INITIAL ratio of the gases is 1:3. that doesn't mean that at equalibrium it will also be 1:3
in this particular question it will, because the equation says that they also react in a ratio of 1:3
but what if let's say, they didn't react in a 1:3 ratio, instead they eg reacted in a 2:3 ratio?
your method only works if they react in the same ratio as well,
but a safer method which would be valid every time would be using algebra:
the number of moles of N2 and H2 at the start is x and 3x
they decrease in the ratio of 1 to 3, so you could say that the number of moles of N2 and H2 at equilibrium is (x - y) and (3x - 3y) respectively, because if N2 decreased in moles by y, then H2 would decrease in moles by 3y.
and because in the reaction equation it says that 2 moles of ammonia are formed,
you could say the number of moles of NH3 are 2y,
the question tells us that the final mole fraction of NH3 at equilibrium is 0.8
therefore you could say that 2y/ the sum of all moles = 0.8
so 2y/((x-y) + (3x-3y) + (2y)) = 0.8

but now i'm stuck because there's 2 unkown terms, and i don't really know what to do.

Can anyone help?

SMH_

Thank you so much for explaining the steps for q 1.1 - I'm studying A-Levels independently and have struggled a lot with born-haber cycles so this is invaluable for me! I will continue to use your videos for revision. Thanks again man!

alextaylor