Buffer solutions and pH curves

Question 1

the buffer range on pH curve is the…………region

Answer 1

the flatter region on the left side of the equivalence point

Question 2

in the buffer range of a pH curve, the pH change is………….and over this range the concentrations of both acid and conjugate base molecules is…………….

Answer 2

gradual change

considerable concentrations of both

Question 3

the experimental method for calculating Ka from a pH curve is:

Answer 3

• titrating a strong base with a weak acid
• plot a graph of pH against the volume of base added
• from the graph, the minimum volume of base required to to completely react with all the acid is determined at the equivalence point
• the pH at the half equivalence point is then calculated as this value is equal to the pKa value of the weak acid
• as Ka = 10 (-pKa) (to the power of)

Question 4

the equation linking Ka and pKa is:

Answer 4

Ka = 10(-pKa)
pKa = -lg Ka