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Topic: What is the equilibrium constant for this reaction?  (Read 441 times)

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Offline Win,odd Dhamnekar

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What is the equilibrium constant for this reaction?
« on: November 21, 2020, 03:18:20 AM »
 How to compute equilibrium constant and equilibrium concentrations of reactants?
« Last Edit: November 21, 2020, 03:29:00 AM by Win,odd Dhamnekar »
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Offline Borek

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Re: What is the equilibrium constant for this reaction?
« Reply #1 on: November 21, 2020, 04:30:45 AM »
This is not much different from other problems you did in the past. Just follow the stoichiometry to find concentrations.

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Offline Win,odd Dhamnekar

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Re: What is the equilibrium constant for this reaction?
« Reply #2 on: November 21, 2020, 11:40:37 PM »
Initial concentration of Reactants [itex]Fe^{3+}= 0.00027 M, (SCN)^{-}=0.00085 M[/itex]. Initial concentration of product [itex]Fe(SCN)^{2+}=0[/itex]. At the equilibrium, concentration of  [itex] Fe(SCN)^{2+}=0.00018=2x[/itex]

[tex]K_c=\frac{0.00018}{(0.00027-x)*(0.00085-x)}=\frac{2x}{(0.00027-x)*(0.00085-x)}\Rightarrow 2x=0.00018,x=0.00009, K_c=\frac{0.00018}{(0.00018)*(0.00076)}=1315.789   liters/mol[/tex]
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Offline AWK

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Re: What is the equilibrium constant for this reaction?
« Reply #3 on: November 22, 2020, 12:58:51 AM »
Why 2x?
AWK

Offline Win,odd Dhamnekar

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Re: What is the equilibrium constant for this reaction?
« Reply #4 on: November 22, 2020, 03:49:01 AM »
Equilibrium concentration of product [itex][Fe(SCN)]^{2+}[/itex] is 2x because one x part we take from [itex]Fe^{3+}[/itex] and anther x part we take from [itex] (SCN)^{-}[/itex]. Adding both, we get 2x.
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Offline Borek

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Re: What is the equilibrium constant for this reaction?
« Reply #5 on: November 22, 2020, 04:26:40 AM »
Equilibrium concentration of product [itex][Fe(SCN)]^{2+}[/itex] is 2x because one x part we take from [itex]Fe^{3+}[/itex] and anther x part we take from [itex] (SCN)^{-}[/itex]. Adding both, we get 2x.

No, you don't add them, that's not how the stoichiometry works.

Please google ICE table and learn what I, C and E stand for and how they are determined.
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Offline Win,odd Dhamnekar

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Re: What is the equilibrium constant for this reaction?
« Reply #6 on: November 22, 2020, 08:40:11 AM »
 Thanks for advice.
Any science consists of the following process.
 1) See 2) Hear 3) Smell if needed 4) Taste if needed
5) Think 6) Understand 7) Inference 8) take decision [Believe or disbelieve, useful or useless, healthy or unhealthy, cause or effect, favorable or unfavorable, practical or theoretical, practically possible or practically impossible, true or false or  any other required criteria]

Offline Win,odd Dhamnekar

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Re: What is the equilibrium constant for this reaction?
« Reply #7 on: November 23, 2020, 03:53:09 AM »
 I prepared ICE table as follows:

Reaction                        Fe³⁺           (SCN)⁻             [Fe(SCN)]²⁺
Initial amounts           0.00027       0.00085                0
Change in amounts    -0.00018      -0.00018           0.00018
Equilibrium amounts   0.00009       0.00067           0.00018

[itex]K_c=\frac{0.00018}{(0.00009)*(0.00067)}=2985.07463 [/itex] liters/mol.   Is this equilibrium constant correctly computed?   
« Last Edit: November 23, 2020, 04:51:05 AM by Win,odd Dhamnekar »
Any science consists of the following process.
 1) See 2) Hear 3) Smell if needed 4) Taste if needed
5) Think 6) Understand 7) Inference 8) take decision [Believe or disbelieve, useful or useless, healthy or unhealthy, cause or effect, favorable or unfavorable, practical or theoretical, practically possible or practically impossible, true or false or  any other required criteria]

Offline mjc123

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Re: What is the equilibrium constant for this reaction?
« Reply #8 on: November 23, 2020, 08:13:07 AM »
Yes, but to an absurd degree of precision, considering that the concentrations are only given to 2 significant figures.

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