September 15, 2019, 06:13:16 AM
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### Topic: equilibrium constant question  (Read 240 times)

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#### roseandmirrors

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• Mole Snacks: +0/-0 ##### equilibrium constant question
« on: July 06, 2019, 02:53:12 PM »
The question : Contain SO2 1 mole, O2 2 moles, SO3 0.5 mol in a close system size 5.0 dm3
Which occurs this reaction 2SO2​ + O2 2SO3 when the system is in equilibrium state, there are SO3 40% by moles. Find out equilibrium constant (k)

I try to solve it :
[SO2] = 1 ÷ 5 = 0.2 M
[O2]​ = 2 ÷ 5 = 0.4 M
[SO3]​ = 0.5 ÷ 5 = 0.1 M

SO3 40% by mole = (1 + 2 + 0.5) × 40% = 1.4 mole
[SO3]​ = 1.4 ÷ 5 = 0.28 M

so..
[SO3] 0.1 + 0.18 = 0.28 M
[SO2]​ 0.2 - 0.18 = 0.02 M
[O2]​ 0.4 - 0.09 = 0.31 M

k = [SO3]​2 ÷ [So2]​2[O2]
​ = (0.28)​2 ÷ (0.02)2(0.31) = 652.26

but my key book said that the answer is 76.9, what is wrong with my way to solve this question?

#### AWK

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« Reply #1 on: July 06, 2019, 03:20:21 PM »
Quote
when the system is in equilibrium state, there are SO3 40% by moles
check oxygen in equlibrium!
AWK

#### roseandmirrors

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• Mole Snacks: +0/-0 ##### Re: equilibrium constant question
« Reply #2 on: July 06, 2019, 04:21:16 PM »
I'm afraid that I still didn't quite get it but thank you so much, I'll try to think about this again in the morning

#### AWK

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« Reply #3 on: July 06, 2019, 04:26:09 PM »
Quote
40% by mole = (1 + 2 + 0.5) × 40% = 1.4 mole
less than 2 moles
AWK

#### roseandmirrors

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• Mole Snacks: +0/-0 ##### Re: equilibrium constant question
« Reply #4 on: July 06, 2019, 05:06:50 PM »
I understand it now. Thank you so much. You are life saver. 🙏