Acids, Bases and Buffer Solutions

Question 1

What is the equation for a neutralisation reaction and where do each of the ions come from?

Answer 1

H+ + OH- –> H2O
H+ = acid
OH- = alkali

Question 2

Give some examples of acids

Answer 2

HCl, HNO3, H2SO4

Question 3

What is H^+ also known as?

Answer 3

A proton

Question 4

What are (Lowry Bronsted) acids in terms of protons?

Answer 4

Proton (H+) donors

Question 5

What are d- elements?

Answer 5

Elements that attract electron more than other elements

Question 6

What are d+ elements?

Answer 6

Elements that attract electrons less than other elements

Question 7

What are H^+(aq) also known as?

Answer 7

H3O+ (aq)

Hydronium ion - with a dative covalent bond between the H+ and the O

Question 8

What is a monoprotic acid?

Answer 8

Acids with one H+ ion

Question 9

What is a diprotic acid?

Answer 9

Acids with two H+ ion

Question 10

What is weaker acid and what does is contain?

Answer 10

Weak acid - doesn’t completely dissociate - reversible

contains - carbon

Question 11

What are bases in terms of protons?

Answer 11

Proton (H+ ) accepters

Question 12

What are some examples of bases?

Answer 12

Alkalis, metal oxides, metal carbonates

Question 13

What are alkalis in terms of bases?

Answer 13

Bases that dissolve in water to produces OH- ion

Question 14

What do all ammonia equations have?

Answer 14

Water

Question 15

What is the symbol for ammonia and its ion symbol?

Answer 15

Ammonia: NH3
Ion: NH4+

Question 16

What assumption do we make about all strong acids?

Answer 16

full dissociation, monoprotic acids

Question 17

What are the equations for pH and [H+]?

Answer 17

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

Question 18

What is the equilibrium of weak acids in water?

Answer 18

HA <–> H+ + A-
eg
CH3COOH <–> H+ + CH3COO-

Question 19

What assumption do we make for weak acids?

Answer 19

[H+] = [A-]
[HA]equilibrium = [HA]start

Question 20

What are the equations for Ka and pKa?

Answer 20

Ka = [H+]^2 / [HA]start
pKa = -log 10 Ka
Ka = 10^(-pKa)

Question 21

What happens if pKa is lowered?

Answer 21

Ka increases - the lower the pKa, the stronger the weak acid

Question 22

What are the [HA] values for strong diprotic and triprotic acids?

Answer 22

diprotic = [H2A]
triprotic = [H3A]

Question 23

What is the assumption of strong bases?

Answer 23

full dissociation
[base]start = [OH-]

Question 24

What if the formula of Kw and what does it equal?

Answer 24

Kw = [H+][OH-]
equals = 10^-14 mol2 dm-6

Question 25

What is the assumption of buffer solutions?

Answer 25

[H+] =/= [A-]

Question 26

What is the calculation for buffer solutions?

Answer 26

Ka = ([H+][A-]) / [HA]

Question 27

When do you recalculate in buffer solutions?

Answer 27

when the volumes are not the same

Question 28

What is the pH of water as 25oC?

Answer 28

7
so [H+] = 10^-7

Question 29

What is a buffer solution?

Answer 29

a solution that resists/opposes change to pH when a small amount of acid or alkali is added

Question 30

What do you need to produce a buffer solution?

Answer 30

1. a weak acid in equilibrium
2. its conjugate base (salt)

Question 31

How does adding H+ affect the HA equilibrium?

Answer 31

initially, pH decreases
equilibrium shifts to the left to decrease [H+]
HA «<–> H+ + A-
[H+] decreases and pH is restored

Question 32

How does adding OH- affect the HA equilibrium?

Answer 32

initially, pH increases
reacts with H+, reducing [H+]
H+ + OH- + H2O
equilibrium shifts to the right to increase [H+] and pH is restored

Question 33

How do you make buffer solutions from weak acids and strong bases?

Answer 33

1. work out moles of weak acid and strong base
2. use ration to find moles of salt produced
3. subtracts off moles of acids reacted to find moles of acid left
4. convert acids and salt moles into concentrations and put into equations