pH

Question 1

what is a proton?

Answer 1

H+ ion

Question 2

what is pH?

Answer 2

logarithmic scale which measures the concentration of H+ ions in a solution

Question 3

how is pH calculated?

Answer 3

-log10[H+]

Question 4

how is [H] from pH calculated?

Answer 4

10-pH

Question 5

what is the assumption of strong acids and bases when calculating pH?

Answer 5

they dissociate fully into H+ and OH- ions

base/acid conc = [ion]

Question 6

calculate the pH for [H] 0.01

Answer 6

-log(0.01 = 2

Question 7

calculate the pH for [H] 16.2x10-13

Answer 7

-log(16.2x10-13 = 11.8

Question 8

calculate the pH for [H] 0.000251

Answer 8

-log(0.000251 = 3.6

Question 9

calculate [H] for pH 3.12

Answer 9

10(-3.12 = 7.59x10-4

Question 10

calculate [H] for pH 6.09

Answer 10

10(-6.09 = 8.13x10-7

Question 11

calculate [H] for pH 12.01

Answer 11

10(-12.01 = 9.77x10-13

Question 12

what is a high pH value in terms of ion concentration?

Answer 12

• 14
• low conc of H+ ions

Question 13

what is a low pH value in terms of ion concentration?

Answer 13

• 0
• high conc of H+ ions

Question 14

what is the strength of an acid?

Answer 14

the extent of its dissociation into H+ and A- ions when in aq solution

Question 15

describe strong acids

Answer 15

• good proton donors
• dissociate completely

Question 16

describe weak acids

Answer 16

• poor proton donors
• partially dissociate
  (reversible arrow in equation)

Question 17

where does equilibrium lie when a weak acid dissociates?

Answer 17

left
- only partially dissociates

Question 18

where does equilibrium lie when a strong acid dissociates?

Answer 18

right
- fully dissociates

Question 19

write the general equation for dissociation of a weak acid

Answer 19

HA <=> H+ + A-

Question 20

state the general Ka expression

Answer 20

[H+] [A-] / [HA]
[products]/[reactants]

Question 21

what does Ka show?

Answer 21

extent of acid dissociation

Question 22

what does a large value of Ka show?

Answer 22

shift of equilibrium to the right
greater dissociation = greater acid strength

Question 23

how is pKa calculated?

Answer 23

-logKa

Question 24

what is pKa?

Answer 24

a way of measuring the strength of an acid similar to pH

Question 25

what does a low pKa tell you?

Answer 25

stronger acid