Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Sunny_Kumar on February 28, 2010, 02:23:03 AM
Title: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
Post by: Sunny_Kumar on February 28, 2010, 02:23:03 AM
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?
Title: Re: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
Post by: Sunny_Kumar on February 28, 2010, 02:28:55 AM
I need help...Please!!!!!!!!!!
Title: Re: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
Post by: Borek on February 28, 2010, 04:36:53 AM
This is a buffer solution and you should use Henderson-Hasselbalch equation (http://www.chembuddy.com/?left=pH-calculation&right=pH-buffers-henderson-hasselbalch).
Title: Re: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
Post by: Sunny_Kumar 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...
Title: Re: Calculating pH of solution of NH4Cl and NH3....Need help please!!!!
Post by: Borek 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.