calculate the change in ph for 1l of buffer solution containing NH4OH and NH4Cl upon addition of 1) 0.02 moles of HCl
2) 0.02 moles of NaOH
I got the initial pH as 9.2504
But now Im stuck cus I dunno what happens when we add HCl and NaOH?
Please help! :)
How did you get the initial pH when you don't know how much base/acid you started with.
Actually I got the pH of initial solution containing NH4OH and NH4Cl. Question is to find the pH change when we add acid and a base respectively. So I know the initial one but dunno what to do after that...
And moles of NH4OH = 0.1
moles of NH4Cl = 0.1
My bad :(
Thanks.
NH4OH initially = 0.1 mol
NH4Cl initially = 0.1 mol
When adding HCl the equation is
......NH3 + H^+ ==> NH4^+
When adding NaOH the equation is and I will do this one.
......NH4^+ OH^- ==> NH3 + H2O
I.....0.1....0.......0.1.......
add........0.02.............
C....-.02..-0.02.....0.02
E....0.08....0.......0.12
Now plug the E line into the HH equation and solve for the new pH. Then find the difference between this new pH and what you found at the beginning.
Adding the acid is the same way. I have used NH3 and not NH4OH. NH4OH actually is NH3 + H2O ==> NH4OH but technically NH4OH doesn't exist.
Oh that worked!
Thank you so much sir!
You literally saved me.
Thanks again :)
To calculate the change in pH for a buffer solution upon addition of acid or base, you need to consider the effect on the concentration of the acidic and basic components of the buffer.
In this case, your buffer solution contains NH4OH (ammonium hydroxide) and NH4Cl (ammonium chloride). Ammonium hydroxide is the base, while ammonium chloride is the corresponding acidic salt.
1) Addition of 0.02 moles of HCl:
HCl is a strong acid that dissociates completely in water. It reacts with the base (NH4OH) in the buffer, resulting in the formation of NH4+ (ammonium ion) and Cl- (chloride ion). The concentration of NH4OH decreases, while the concentration of NH4+ increases.
To calculate the change in pH, you can use the Henderson-Hasselbalch equation, which for a basic buffer solution is:
pH = pKa + log ([salt] / [base])
In this case, the concentration of the base decreases by 0.02 moles (because it reacts with HCl), and the concentration of the salt (NH4Cl) increases by 0.02 moles. The initial pH value you provided (9.2504) indicates that the pOH is 4.7496. To find pKa, subtract the pOH from 14:
pKa = 14 - pOH = 14 - 4.7496 = 9.2504
Using the Henderson-Hasselbalch equation:
pH = 9.2504 + log ([NH4Cl] / [NH4OH])
To find the concentrations of NH4Cl and NH4OH, you need to know the initial volumes or concentrations of these components in the 1L buffer solution.
2) Addition of 0.02 moles of NaOH:
NaOH is a strong base that also dissociates completely in water. It reacts with the acid component (NH4Cl) of the buffer, resulting in the formation of NH3 (ammonia) and NaCl.
Similar to the previous case, the change in pH can be calculated using the Henderson-Hasselbalch equation. The concentration of NH4Cl decreases by 0.02 moles, and the concentration of NH3 (formed from the reaction) increases by 0.02 moles.
Use the Henderson-Hasselbalch equation:
pH = 9.2504 + log ([NH3] / [NH4Cl])
To find the concentrations of NH3 and NH4Cl, you need to know the initial volumes or concentrations of these components in the 1L buffer solution.
Remember that these calculations require the initial concentrations or volumes of the components in the buffer solution.