Exam 1: Chapter 2 - Waters and Buffers

Question 1

how to find concentration of [H+] or [OH-] given one of the values above

Answer 1

𝐾w = [H+][OH−] = 1×10−14 M

Question 2

how to find Ka given pKa = 4.76

Answer 2

Ka = 10^-4.76

Question 3

What does a larger Ka indicate?

Answer 3

larger (more positive Ka) indicate a stronger acid

Question 4

how to find conjugate base

Answer 4

take away H+, add electron

Question 5

how to find conjugate acid

Answer 5

add H+, delete electron

Question 6

How to calculate concentration ratio ([A-]/[HA]) given pka = 3.86 and pH = 4.25

Answer 6

4.25 = 3.86 + log [ratio], then 0.39 = log [ratio], then 10^0.39 = 2.45

Question 7

Find pKa given [A-], [HA], [H+]

Answer 7

Ka = [A-][HA] / [H+]
then pka = -log (ka)

Question 8

What is the [H+] given pH = 9.75

Answer 8

10^-9.75

Question 9

What is the pH given [A-] and [HA] and given Ka or pKa

Answer 9

pH = pKa + log (ratio)
if given Ka, find pKa using pKa = -log(ka)
then pH = pKa + log (ratio)