chemistry aqa a level equilibrium question]

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sierranonis
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Could someone help me with 2b please ? Thank you .
CH3COOH + CH3CH2OH CH3COOCH2CH3 + H2O

1.00 moldm-3 of acid is reacted with 0.330 moldm-3 of alcohol. At
equilibrium 0.293 moldm-3 of ester is present. Calculate Kc.

2a) When 1 mol each of ethanoic acid and ethanol are mixed together at a
fixed temperature 0.333 mol of acid remain at equilibrium. Calculate the
value of Kc at this temperature.

2b) At the same temperature the equilibrium mixture contains 0.142 mol of
ethanoic acid and 1.142 mol of ethanol. Calculate the amount of ester
present in this equilibrium mixture, assuming that none was present initially.
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Pyruvic Acid
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What have you done so far?
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sierranonis
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I did 2a and got an answer of 4.012 ( no units)
Then the equilibrium moles for 2b of ethanoic acid is 0.142 and 1.142 for ethanol , I wrote the moles for water and the ester as x
Kc = X x X / 0.142 x 0.142
X2= Kc x 0.162164
But the mark scheme says Kc is 4.102 ( from 2a) , but I don't understand why how question 2a and 2b link. Thanks.
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pwk123
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(Original post by sierranonis)
I did 2a and got an answer of 4.012 ( no units)
Then the equilibrium moles for 2b of ethanoic acid is 0.142 and 1.142 for ethanol , I wrote the moles for water and the ester as x
Kc = X x X / 0.142 x 0.142
X2= Kc x 0.162164
But the mark scheme says Kc is 4.102 ( from 2a) , but I don't understand why how question 2a and 2b link. Thanks.
As it says 2b is conducted at the same temperature therefore Kc must also be the same
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sierranonis
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Thank you , I figured it out but tyyy!
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