Hydrolysis, buffers and volumetric analysis

Question 1

Salt

Answer 1

Ionic compound consisting of a cation (other than H+) and an anion (other than OH- or O2, Metal and a non-metal, Formed in neutralisation reactions by the combination of an acid with a base

Question 2

Strong acid + strong base

Answer 2

Produces a neutral salt because both the cation and anion are neutral

Question 3

Strong acid + weak base (Ammonia)

Answer 3

Produces an acidic salt due to the hydrolysis of the NH4+ ion

Question 4

Weak acid + strong base (Acetic acid)

Answer 4

Produces a basic salt due to the hydrolysis of CH3COO-

Question 5

Weak acid + weak base

Answer 5

Can’t say whether the salt is acidic or basic as both the cation and anion can hydrolyse

Question 6

Buffers

Answer 6

Solutions which resist (partially counteracts) changes in pH on dilution or on the addition of a small amount of acid or alkali, Protect animals and plants against changes in pH, Consist of a weak acid and it’s conjugate base or a weak base and it’s conjugate acid- can’t be strong as they completely ionise meaning resulting in a complete reaction not an equilibrium system

Question 7

Buffering capacity

Answer 7

Number of moles of a strong acid or base needed to change the pH of a litre of buffer solution by 1 pH unit

Question 8

Perfect buffer (not found in biological buffers)

Answer 8

High concentration of the weak acid and it’s conjugate base or weak base or it’s conjugate acid (reduces chance of running out), Concentrations of the acid and it’s conjugate base or base and it’s conjugate acid are equal (means no limiting reagent)

Question 9

Buffer broke

Answer 9

Used all the buffer, no more acid/base

Question 10

Primary standard criteria

Answer 10

Be pure with a known formula, Shouldn’t alter by absorbing or losing water or reacting with air, High formula mass- minimise errors

Question 11

Indicators

Answer 11

Weak acid or base, PH sensitive, Acid and conjugate base/ base and conjugate acid are different distinct colours

Question 12

Equivalence

Answer 12

when you have stoichiometric equivalent amounts of acid and base (Kind of like mole—> mole ratio

Question 13

Endpoint

Answer 13

when the indicator changes colour (when you end the reaction)

Question 14

Methyl Orange

Answer 14

Changes at pH of 3.7 (acidic), red to orangey yellow

Question 15

Bromothymol Blue

Answer 15

Changes at pH of 7.5 (neutral), yellow to blue

Question 16

Phenolphthalein

Answer 16

Changes at a pH of 9.3 (basic), colourless to pink