Calculate the pH of a buffer that is 0.321 NH_3 AND 0.123M NH_4Cl.
This solution is a buffer solution. And a buffer solution is one which maintains a fairly constant pH.
Kb for NH3 = 1.8 x 10^-5 from literature
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Question & Answer: Calculate the pH of a buffer that is 0.321 NH_3 AND 0.123M NH_4Cl……
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Calculate PKb from Kb
pKb = -log Kb
pKb = -log 1.8 x 10^-5
By using Henderson-Hassel Balch Equation for base.
Given Conc of NH3= 0.321 M & NH4Cl = 0.123 M
pOH = pKb + log10 (BH+ / B )
pOH = 4.7447 + log(0.123 / 0.321 )
pOH = 4.7447 + log(0.3831) = 4.7447 – 0.4166
pOH = 4.33
We know PH + pOH =14
pH =14 – 4.33
pH = 9.67