Lab 9 - pH, pKa & Buffers Flashcards
1
Q
Define buffer
A
A buffer is an aqueous solution containing a weak acid and its conjugate base or a weak base and its conjugate acid.
2
Q
Ka formula
A
Ka = [H+][A-] / [HA]
3
Q
Henderson Hasselbalch equation
A
pH = pKa + log ([salt] / [acid])
4
Q
pH = pKa indicates
A
the best buffer capacity
5
Q
Why do some acids have several pKa?
A
Depending on the number of hydrogen
6
Q
Prepare 200ml of acetate buffer at pH=6 with molar concentration of 0.4M, knowing that the ka value for acetic acid is 1.8 × 10‐⁵
A
Find the ratio of salt to acid
Find the weight of the acid and the salt need to be used
Weight = mole fraction × concentration × molecular weight × volume (L)
Mix of both of these salts with water till 200ml in a conical flask
7
Q
Determination of Kpa
A
Check slide 11/12 in the ppt.
