Calculating the pH of a Basic Buffer Part A An ammonia/ammonium buffer solution

Question

Calculating the pH of a Basic Buffer

Part A

An ammonia/ammonium buffer solution contains 0.32 M NH3 and 0.86 M NH4+. The Kb value of ammonia is 1.8×105. Calculate the pH of this buffer.

Express the pH numerically.

Calculating the pH of an Acid Buffer

Part A

A lactic acid/lactate ion buffer solution contains 0.10 M HC3H5O3 and 0.69 M C3H5O3, respectively. The Ka value of lactic acid is 1.4×104. Calculate the pH of this buffer.

Express the pH numerically.

Preparing Buffer Solutions

Part A

What substance would you add to KF(aq) to form a buffer solution?

Explanation / Answer

pH of basic buffer

Part A : Using Hendersen-Hasselbalck equation,

pH = pKa + log([base]/salt])

Ka = Kw/Kb = 1 x 10^-14/1.8 x 10^-5 = 5.55 x 10^-10

pKa = -logKa = 9.255

with,

[base] = 0.32 M

[salt] = 0.86 M

we get,

pH = 9.255 + log(0.32/0.86) = 8.826

pH of acidic buffer

Part A : Again using Hendersen-Hasselbalck equation,

pKa = -log(1.4 x 10^-4) = 3.854

[base] = 0.69 M

[acid] = 0.10 M

we get,

pH = 3.854 + log(0.69/0.1) = 4.693

Preparing buffer solution

Part A : To prepare a buffer with KF we would add,

HF

So it would be conbination of weak acid HF and strong base KF

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.