18.3 pH

Question 1

How is a buffer prepared?

Answer 1

• Mixing a solution of weak acid/base with a Salt containing its conjugate (NaCH3COO)

Question 2

How is a buffer solution affected by Dilution?

Answer 2

No effect. Dilution does not change the ratio of acid or base to salt concentration, as both decreases equally

Question 3

What is a buffering capacity?

Answer 3

the ability of a buffer to absorbe H or OH whiteout a drastic change in pH

Question 4

How is a buffer solution affected by Temperature?

Answer 4

Affects the values of Ka and Kb, so it does affect pH of the buffer.

Question 5

Salts of Strong Acid + Strong Base

Answer 5

• no hydrolysis
• since both conjugate acid and bases are weak
• pH 7

Question 6

Salts of Weak Acid + Strong Base

Answer 6

• anion hydrolysis (OH-)
• Conjugate base of the weak acid is strong enough to hydrolyze water
• the strong conjugate base forcefully yanks a H from water leaving OH behind
• pH > 7

Question 7

Salts of Strong Acid + Weak Base

Answer 7

• Cation Hydrolysis (H+)
• Conjugate acid of the weak base is strong enough to hydrolyze water
• yanks OH from water leaving H+ behind
• pH < 7

Question 8

Salts of Weak Acid + Weak Base

Answer 8

• Cation & Anion Hydrolysis
• Both strong conjugate acid and bases strip water
• pH cannot be generalized and depends on Ka and Kb of conjugates

Question 9

What is an equivalence point ?

Answer 9

point where all the acid or baes titrate are neutralized

Question 10

Which acid base reaction have a buffer region?

Answer 10

Weak acid and strong base

Question 11

Where is the Equivalence point for a weak acid strong base reaction and why?

Answer 11

pH > 7 Strong conjugate base of the weak acid hydrolyses OH ions

Question 12

Where is the Equivalence point for a strong acid weak base reaction and why?

Answer 12

pH < 7 Strong conjugate acid of the weak base hydrolyzes H ions

Question 13

Where is the Equivalence point for a weak acid weak base reaction and why?

Answer 13

hard to pinpoint using a graph

Question 14

Draw me all the pH graphs :)

Answer 14

0_0

Question 15

what is an indicator?

Answer 15

Weak acids or weak bases in equilibrium that have different colour for reactants and products.
- the equilibrium will shift left or right depending on contact with acid or base and change colour

Question 16

When do indicators change colours?

Answer 16

When pH is equal to their pKa

Question 17

What is the end point?

Answer 17

• The point at which the conjugate acid base pair of an indicator is equal to each other
• a small subsequent drop of acid or base will shift equilibrium one way and change colour