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Topic: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!  (Read 34802 times)

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Offline Sunny_Kumar

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Calculate the pH of solution formed on mixing 0.2M NH4Cl and 0.1M NH3. The pKb of ammonia solution is 4.75.

I want to know that if we consider concentration of NH4+ obtained from NH3 to be x, then will total concentration of H+ be 0.2 + x????
Does that mean we are considering complete dissociation of NH4CL into its ions??? Will NH4+ ions formed be also included in pH as H+ ions????


Second Question:


If this is so, then will hydrazinium ions formed during dissociation of 0.004M hydrazine be included in its pH?

Offline Sunny_Kumar

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Re: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
« Reply #1 on: February 28, 2010, 02:28:55 AM »
I need help...Please!!!!!!!!!!

Offline Borek

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Re: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
« Reply #2 on: February 28, 2010, 04:36:53 AM »
This is a buffer solution and you should use Henderson-Hasselbalch equation.
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Offline Sunny_Kumar

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Re: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
« Reply #3 on: February 28, 2010, 07:54:47 AM »
W e haven't studied any such equation so far and i don't believe its in our course right now..

Can you explain it using a simple method like taking the dissociated amount as x or something...pls...

Offline Borek

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Re: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
« Reply #4 on: February 28, 2010, 11:28:30 AM »
Basically Henderson-Hasslebalch equation is just a dissociation constant definition transformed into another form. Trying to solve the question differently is a waste of time.
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