3.1.12: Acids and bases

Question 1

What is a bronsted-lowry acid?

Answer 1

proton donor

Question 2

What is a bronsted-lowry base?

Answer 2

proton acceptor

Question 3

What is the difference between a monoprotic and diprotic acid?

Answer 3

• monoprotic- acids releasing one H+
• diprotic- acids releasing 2 H+

Question 4

What is the equation for pH and [H+]?

Answer 4

pH= -log [H+]
[H+]= 10^-pH

Question 5

What is the equation for the dissociation of water?

Answer 5

H2O ⇌ H+ + OH-
▲H= endothermic

Question 6

What is Kw?

ionic product of water

Answer 6

Kw= [H+][OH-]
(no H2O as conc. of water in water is 1)

Question 7

Why is the pH of water at room temperature 7?

Answer 7

• pH of water= 7
• [H+] and [OH-]= 10^-7
• Kw @ 25°C= 10^-14

Question 8

Why is water neutral?

Answer 8

has the same concentration of hydrogen and hydroxide ions
[H+] = [OH-]

Question 9

How does temperature effect pH and the neutrality of water?

Answer 9

• as temperature increases, equilibrium shifts to endothermic direction to oppose the change in temperature
• therefore [H+] and [OH-] increase, Kw increase and pH decrease
• water still neutral as [H+] = [OH-]

Question 10

What is Ka?

acid dissociation constant

Answer 10

Ka= ([H+][A-]) ÷ [HA]
or
Ka= [H+]^2 ÷ [HA] in pure weak acids ONLY

Question 11

What is the equation for pKa and Ka?

Answer 11

pKa= -log Ka
Ka = 10^-pKa

Question 12

What is the equation for the dissociation of acid?

Answer 12

HA ⇌ H+ + A-
▲H= endothermic

Question 13

How are Ka and pKa used to determine acid strength?

Answer 13

• the larger Ka. the smaller the pKa value, and the stronger the acid
• the lower the Ka value, the higher the pKa value, and the weaker the acid

Question 14

What is the definition of a strong and weak acid?

Answer 14

• strong acid- all molecules fully ionise/ dissociate in water
• weak acid- only partially ionises/dissociates in water

Question 15

What’s a pH indicator?