Acids and Bases

Question 1

Weak acids

Answer 1

• Do not fully ionise in solution
• Equilibrium lies closer to the middle, compared to strong acids who lie far to the right

Question 2

Weak bases

Answer 2

• Do not fully ionise in solution

Question 3

Ka

Answer 3

• Ka = [H+] x [A-] / [HA]
• Large Ka value means a lot of acid ionises in the solution
• Ka = 10-pKa

Question 4

pKa

Answer 4

• pKa = -log (Ka)
• similar to pH
• used for weak acids

Question 5

Calculating [H+] from Ka

Answer 5

• [H+] is always equal to [A-]
• Ka = [H+]2 / [HA]

Question 6

Calculating [HA] from Ka and pH

Answer 6

• First calculate [H+] from pH
• Rearrange Ka equation to [HA] = [H+]2 / Ka

Question 7

What is a buffer solution?

Answer 7

• a solution that opposes pH change
• if you add acid, the buffer solution removes it to keep a constant pH

Question 8

How do buffer solutions work?

Answer 8

• through changes in equilibria
• an acidic buffer contains a weak acid and the salt of the weak acid