September 18, 2024, 08:59:48 PM
Forum Rules: Read This Before Posting

### Topic: To find equilibrium constant from rate constant  (Read 5350 times)

0 Members and 1 Guest are viewing this topic.

#### Zeeshan Manzoor

• New Member
• Posts: 8
• Mole Snacks: +0/-0
##### To find equilibrium constant from rate constant
« on: May 27, 2017, 12:04:55 PM »
I have problem in a physical chemistry practical. My teacher asked me to calculate the equilibrium constant of acid hydrolysis of ethyl acetate using conductometer. I have calculated rate constant and activation energy by performing this practical using formula:
L= 1/CoK(Lo-L)/t)+Lo
As far as i know the relationship between equilibrium constant and rate constant, it is Kc= Kf/Kr
but still i have a problem that i know only one rate constant. How can i solve it?
« Last Edit: May 28, 2017, 03:43:03 PM by Arkcon »

#### Corribus

• Chemist
• Sr. Member
• Posts: 3526
• Mole Snacks: +540/-23
• Gender:
• A lover of spectroscopy and chocolate.
##### Re: TO FIND EQUILIBRIUM CONSTANT FROM RATE CONSTANT
« Reply #1 on: May 27, 2017, 08:46:57 PM »
Can you define the parameters in your first equation?
The equilibrium constant can be determined by the ratio of the forward and backward rates, or the standard Gibbs energy change, or via the relative concentrations of each species at equilibrium.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

#### Zeeshan Manzoor

• New Member
• Posts: 8
• Mole Snacks: +0/-0
##### Re: TO FIND EQUILIBRIUM CONSTANT FROM RATE CONSTANT
« Reply #2 on: May 28, 2017, 04:08:55 AM »
In equation L= 1/CoK(Lo-L)/t)+Lo
L is conductivity of solution measured by conductometer
Co is initial concentration of solution
Lo is conductivity of solution at initial concentration
t is time of reaction

#### Corribus

• Chemist
• Sr. Member
• Posts: 3526
• Mole Snacks: +540/-23
• Gender:
• A lover of spectroscopy and chocolate.
##### Re: TO FIND EQUILIBRIUM CONSTANT FROM RATE CONSTANT
« Reply #3 on: May 28, 2017, 12:23:19 PM »
Although I haven't read your experimental protocol, my suspicion is that you are intended to determine the equilibrium constant via method 3 (relative concentrations of all species at equilibrium), not via method 1 (forward and backward rates). Monitoring the conductivity as a function of time is mostly so you know when equilibrium has been reached (when the conductivity no longer changes), not so you can calculate a rate constant.

If all this is the case, the trick is for you to determine how you can calculate the concentration of all the reactants/products in solution at equilibrium.

Toward that end, I would start with writing a balanced equation for the reaction as well as an expression to determine the equilibrium constant from the equilibrium concentrations. Not only will the first part be critical toward the second part, but it will also help you answer the third critical question: why does the conductivity change as the reaction proceeds, and how do you relate that to equilibrium concentrations of products and reactants?

Did your teacher give you any guidance at all about how to go about solving this problem?
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

#### Zeeshan Manzoor

• New Member
• Posts: 8
• Mole Snacks: +0/-0
##### Re: TO FIND EQUILIBRIUM CONSTANT FROM RATE CONSTANT
« Reply #4 on: May 28, 2017, 02:19:52 PM »
NO, he did not guide anything about it.
can you please explain me that how can i calculate concentration or number of moles at equilibrium using conductivity?

#### Borek

• Mr. pH
• Deity Member
• Posts: 27789
• Mole Snacks: +1805/-411
• Gender:
• I am known to be occasionally wrong.
##### Re: TO FIND EQUILIBRIUM CONSTANT FROM RATE CONSTANT
« Reply #5 on: May 28, 2017, 04:00:50 PM »
In equation L= 1/CoK(Lo-L)/t)+Lo
L is conductivity of solution measured by conductometer
Co is initial concentration of solution
Lo is conductivity of solution at initial concentration
t is time of reaction

And what is K?

The formula you have posted is wrong - there are two closed parentheses, but only one opened. Try to format the formula with Latex, as explained here.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

#### Corribus

• Chemist
• Sr. Member
• Posts: 3526
• Mole Snacks: +540/-23
• Gender:
• A lover of spectroscopy and chocolate.
##### Re: TO FIND EQUILIBRIUM CONSTANT FROM RATE CONSTANT
« Reply #6 on: May 28, 2017, 06:08:39 PM »
NO, he did not guide anything about it.
can you please explain me that how can i calculate concentration or number of moles at equilibrium using conductivity?
Start by writing a balanced reaction and see if you can relate either products or reactants to a change in conductivity.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman