Background Knowledge

Question 1

Draw the graphs if rate against concentration for 0 order, 1st order and 2nd order

Answer 1

See notes page 47 rev book
0 = straight line across
1st = straight line through origin
2nd = curve upwards

Question 2

Draw the graphs of 0 order, 1st order and 2nd order for concentration against time

Answer 2

See notes page 48 rev book
0 = straight line going down
1st = downwards curve
2nd = deeper downwards curve

Question 3

What is an acidic buffer made up of and what is an alkaline buffer made up of

Answer 3

Weak acid and its salt

Weak base and its salt

Question 4

What is the definition of a buffer

Answer 4

A solution which resists changes in pH upon addition of small amounts of acid or alkali

Question 5

What is the equation for pH (both normal and Henderson-Hasselbalch)

Answer 5

See unit 1 notes

Question 6

What is the equation and value of kw

Answer 6

(H+)(OH-)

1x10^-14

Question 7

What is the equation of pkw

Answer 7

-log(kw)

Question 8

What is the equation for Ka and pka

Answer 8

(H+)^2 ➡️ or (H+)(A-)
————
(HA)

-log(Ka)

Question 9

Draw the titration curves for a strong acid and strong base, weak acid strong base, strong acid weak base and a weak acid weak base

Answer 9

See pg 54 rev book

Question 10

What colour is the precipitate when an aldehyde or ketone is added to 2,4-dinitrophenylhydrazine

Answer 10

Yellow/orange

Question 11

Why is excess aldehyde/ketone added to 2,4-dinitrophenlyhydrazine rather than the other way round

Answer 11

The solid 2,4-dinitrophenylhydrazone is soluble in propanone and other aldehydes and ketones

Question 12

What are the requirements of a solvent

Answer 12

Impurities have to be either insoluble in the solvent or very soluble - so they either do not dissolve or stay dissolved even when the filtrate is cooled

Question 13

Draw the diagram for suction filtration

Answer 13

See pg 58 rev book

Question 14

What is the colour change for Fehling’s solution test

Write the half equation

Answer 14

Blue to red precipitate

Cu^2+ ➕ e- ➡️ Cu^+

Question 15

What is the colour change for Tollens’ reagent

Write the half equation

Answer 15

Colourless to silver mirror

Ag^+ ➕ e- ➡️ Ag

Question 16

Why is sulfuric acid used in an esterification reaction

Answer 16

Catalyst

Removes water - shifts equilibrium to the right - more Ester formed

Question 17

Why are acyl chlorides better for esterification than carboxylic acids

Answer 17

No catalyst needed
Irreversible
Reaction goes to completion

Question 18

What is a nitrating mixture made from

Answer 18

Concentrated sulfuric acid and concentrated nitric acid

Question 19

Why is the base line in chromatography drawn in pencil

Answer 19

Not soluble in the solvents used

Question 20

Why are iodine crystals used as a locating agent for TLC

Answer 20

The iodine vapour can adhere to the spots and mark them

Question 21

What are the standard conditions for the standard electrode

Answer 21

25°C (298K)
100kPa (1atm)
1 mol dm^-3 concentration if ions for the solution

Question 22

Why is a high resistance voltmeter used when determining electrode potentials

Answer 22

Measure voltage but not allow any current to flow

Question 23

How do you make a salt bridge

Answer 23

Filter paper soaked in a concentrated solution of potassium chloride or potassium nitrate

Question 24

Write the equation for the formation of aspirin

Answer 24

See notes page 82 rev book

Question 25

Why is suction filtration preferred to gravity filtration

Answer 25

Faster and gives a drier product

Question 26

Why is phosphoric acid used in the production of aspirin

Answer 26

Acts as a catalyst

Question 27

Why is water added afterwards in the formation of aspirin

Answer 27

To hydrolyse any remaining ethanoic anhydride

Question 28

How do you test the purity after producing aspirin and what is observed if there are/aren’t impurities

Answer 28

Add a solution if iron(III) chloride
A purple colour will be observed
If no impurities then it will remain yellow/orange