Acids and Bases

Question 1

what is the Bronsled-lowry principle?

Answer 1

acid is a substance that donates a proton (H+) base is a substance that accepts a proton

Question 2

what does [H+] indicate?

Answer 2

concentration of H+ in a solution

Question 3

HCl→H⁺ + Cl⁻, what is the acid/conjugate base pair?

Answer 3

HCl/Cl⁻

Question 4

what does it mean to be a strong acid or base?

Answer 4

Completely dissociates in a solution.

Question 5

what is the strength of an acid dependant on?

Answer 5

concentration of acid, equilibrium constant, degree of ionisation (dissociation)

Question 6

for strong acids what is Ka?

Answer 6

Ka = products/reactants, size of Ka = strength of acid

Question 7

how do we calculate pH for an acid?

Answer 7

-log10[H₃O⁺]

Question 8

How do we calculate the pH of a base?

Answer 8

pOH= -log10[OH⁻] 14-pOH=pH

Question 9

how do we find the concentration?

Answer 9

using pH we can use 10⁻pH or using pOH 10⁻pOH

Question 10

What is the equation for Kw?

Answer 10

[H₃O⁺] x [OH⁻] = 10⁻¹⁴ pH + pOH = 14

Question 11

as you increase the pH the number of H⁺ ions goes….

Answer 11

down

Question 12

whats the relationship between Ka and Kb?

Answer 12

Kb = Kw/Ka (Kw = 1x10⁻¹⁴)

Question 13

how do we calculate pKa and pKb?

Answer 13

-log10Ka, -log10Kb

Question 14

whats the relationship between pKa and pKb?

Answer 14

pKa + pKb = 14

Question 15

How do we calculate Ka and Kb?

Answer 15

10⁻pKa or 10⁻pKb

Question 16

what does it mean if there is a small pKa value?

Answer 16

the stronger the acid, the smaller the value of pKa

Question 17

what is the general equation for [H₃O⁺]?

Answer 17

[H₃O⁺] = √Ka x (conc acid) → pH = ⁻log10[H₃O⁺]

Question 18

what is the general equation for [OH⁻]?

Answer 18

[OH⁻] = √Kb x (conc base) → pOH = ⁻log10[OH⁻] → 14 - pOH = pH

Question 19

what is a neutral salt solution?

Answer 19

anion and cation are from a strong acid and base e.g NaCl(s) → Na⁺(aq) + Cl⁻(aq)

Question 20

what is a acidic salt solution?

Answer 20

Anion is from a strong acid and cation from a weak base
e.g.
NH₄Cl (s) → NH₄⁺ (aq)+ Cl⁻(aq)
NH₄⁺(aq) + H₂O(aq) ⇌ NH₃ (aq)+ H₃O⁺(aq)

Question 21

what is a basic salt solution?

Answer 21

Anion from a weak acid and Cation from a strong base
e.g.
CH₃COONa (s) → CH₃COO⁻ (aq)+ Na⁺ (aq)
CH₃COO⁻ (aq) + H₂O (aq) ⇌ CH₃COOH (aq)+ OH⁻ (aq)

Question 22

what does a buffer solution do?

Answer 22

minimise pH change when [H⁺] ions are added (or removed by addition of a base)

Question 23

what is a buffer solution?

Answer 23

a weak acid and its conjugate base

Question 24

what is the significance of equilibrium in:
HA (aq) ⇌ H⁺ (aq) + A⁻ (aq)

Answer 24

weak acid ands conjugate base are in excess, the equilibrium between them are not sensitive to changes. This means it will be very sensitive to changes in the concentration of H⁺ (aq) ions.

Question 25

What happens when H⁺ (aq) ion concentration is increased or decreased?

Answer 25

The position of equilibrium moves to oppose the change

Question 26

whats the pH calculation for a buffer?

Answer 26

pH = pKa + log [A⁻]/[HA]

Question 27

what happens if [HA] = [A⁻]

Answer 27

this means pH = pKa, theyre the same

Question 28

what happens if [HA]>[A⁻]?

Answer 28

This means there is more acid than conjugate base, pH of buffer will be less than pKa. The buffer will have a bigger capacity to neutralise base than acid (it can still do both but just able to add more base)

Question 29

what happens if [HA]<[A⁻]?

Answer 29

This means there is more conjugate base than acid, the pH of buffer will be more than pKa. The buffer will also have a bigger capacity to neutralise acid.

Question 30

Whats the point of titration?

Answer 30

used to find the unknown concentration of an acid or base by reacting it perfectly with a base or acid of a known concentration

Question 31

what is the end point?

Answer 31

the point at which an indicator changes colour at a certain pH (should be as close as possible to equivalence point)

Question 32

What is the equivalence point?

Answer 32

the point where acid and base have reacted together and theres no amount of either left over.

Question 33

How do we find the initial concentration of a weak acid? [Ha] ⇋ [H⁺] + [A⁻]

Answer 33

[HA] = ([H⁺]/Ka) + [H⁺]