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# Kc ques - confused Watch

1. Confused on ques 2.c)
So i worked out thre units to be mol-1dm3 which is wrong. You have one product at the top and 2 reactants at the bottom so you gwt 1 over moldm-3 which i reversed to get mol-1dm3

For part c i got 0.036^2 divided by [SO2]^2 × 0.18 = 15
Rearranging i got sq root of 0.18 x 15 al divided by 0.036^2 which is wrong. In the answer they have the fraction reversed. Help please Attachment 505551505557
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2. (Original post by kiiten)
Confused on ques 2.c)
So i worked out thre units to be mol-1dm3 which is wrong. You have one product at the top and 2 reactants at the bottom so you gwt 1 over moldm-3 which i reversed to get mol-1dm3

For part c i got 0.036^2 divided by [SO2]^2 × 0.18 = 15
Rearranging i got sq root of 0.18 x 15 al divided by 0.036^2 which is wrong. In the answer they have the fraction reversed. Help please Attachment 505551505557
I thought Kc was constant regardless of concentration of products or reactants as the position of equilibrium shifts to counteract any change in concentration? I'll give you a free bump as i'm equally as puzzled.
3. (Original post by BioStudentx)
I thought Kc was constant regardless of concentration of products or reactants as the position of equilibrium shifts to counteract any change in concentration? I'll give you a free bump as i'm equally as puzzled.
Kw is always constant, Kc doesnt have to be
4. (Original post by samb1234)
Kw is always constant, Kc doesnt have to be
Whats kw
5. (Original post by kiiten)
Whats kw
Ionic product of water, basically its the equilibrium constant for 2 H2O <-> h3o+ + oh-
6. (Original post by samb1234)
Ionic product of water, basically its the equilibrium constant for 2 H2O <-> h3o+ + oh-
I thought Kc only changed with temperature. Changes in concentration doesn't affect it. At least that's what my A level ocr text book states.
7. (Original post by BioStudentx)
I thought Kc only changed with temperature. Changes in concentration doesn't affect it. At least that's what my A level ocr text book states.
Sorry yeah i misread what you wrote. It doesnt make a difference to the question, its just a hypothetical question to get you to manipulate the kc equation ther way around, probably because they are lazy and couldnt be bothered to write a whole new question with the Kc is ... Work out conc of x
8. Kw changes with temp.

Soz.
9. looking for unknown SO2 concentration so rearrange equation to get [SO2]2= [SO3]2 / Kc x [O2]

sub in known values [SO2]2 = [0.36]2 / 15 x [0.18]
[SO2]2 = 0.048
[SO2]= 0.219 or 0.22
10. (Original post by GO97)
looking for unknown SO2 concentration so rearrange equation to get [SO2]2= [SO3]2 / Kc x [O2]

sub in known values [SO2]2 = [0.36]2 / 15 x [0.18]
[SO2]2 = 0.048
[SO2]= 0.219 or 0.22
Thanks

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11. (Original post by GO97)
looking for unknown SO2 concentration so rearrange equation to get [SO2]2= [SO3]2 / Kc x [O2]

sub in known values [SO2]2 = [0.36]2 / 15 x [0.18]
[SO2]2 = 0.048
[SO2]= 0.219 or 0.22
What about the units i got 1/moldm-3 which is mol-1dm3 but in the book it says moldm-3 ???

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12. (Original post by kiiten)
What about the units i got 1/moldm-3 which is mol-1dm3 but in the book it says moldm-3 ???

Posted from TSR Mobile
could be a mistake in the answer scheme, is the answer i got to correct? if so then 1/moldm-3 or mol-1dm3 is definetly right.

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