Learning from mistakes

Question 1

coproduct vs byproduct

Answer 1

coproducts are formed in the main reaction along with the desired product. byproducts are formed in unwanted side reactions.

Question 2

sulfonate vs sulfonyl

Answer 2

sulfonate is charged (SO3-)

sulfonyl is not charged (SO3H)

Question 3

solubility of Pb2+ salts

Answer 3

all insoluble and a white ppt apart from lead iodide, which is bright yellow, and lead nitrate, which is soluble.

Question 4

effect of changing pressure on Kc

Answer 4

no change in the size of Kc

Question 5

equation for the formation of the electrophile in nitration

Answer 5

2 H2SO4 + HNO3 => H3O+ + NO2+ + 2 HSO4-

Question 6

how to obtain a pure sample of an organic solid from a reaction mixture

Answer 6

filter then recrystallise

Question 7

is concentrated or dilute sulphuric acid required for esterification/

Answer 7

concentrated

Question 8

why is a diphenol more reactive than benzene so doesn’t require a catalyst (for friedel craft’s alkylation)

Answer 8

lone pairs of electrons from the OH groups become delocalised into the pi system, increasing electron density and making the diphenol more susceptible to electrophilic attack.

Question 9

naming a carboxylic acid alkene

Answer 9

-enoic acid

Question 10

3 methods for usefully processing waste polymers

Answer 10

• recycling
• combustion for energy production
• use as organic feedstock for plastic production

Question 11

method for distillation and purification of an organic liquid

Answer 11

• shake and leave to settle in separating funnel
• separate layers by tapping off
• add a small amount of anhydrous sodium sulphate to the organic layer in a dry conical flask, then filter
• distil the organic layer, collect the fraction below and up to the boiling point of the liquid.

Question 12

why may the theoretical yield for a reaction not be obtained? (5)

Answer 12

Loss of product from reaction vessels 
Side reactions occurring 
Impurities in reactants 
Changes in temp and pressure 
Reaction is an equilibrium system

Question 13

solubility of nitrates

Answer 13

all nitrates are soluble

Question 14

which cations always form soluble salts

Answer 14

Li+, Na+, K+, NH4+

Question 15

solubility of Na+, Li+ and K+ salts

Answer 15

always soluble

Question 16

solubility of sulphate salts

Answer 16

Ca2+, Ba2+ and Pb2+ all form white precipitates, the rest are soluble

Question 17

solubility of hydroxide salts

Answer 17

groups 1 and 2 are soluble, the rest are insoluble. solubility of group 2 hydroxides increases down the group

Question 18

solubility of carbonate salts

Answer 18

Li+, Na+, K+, NH4+ are all soluble
the rest are insoluble:
Ca2+, Ba2+, Fe2+, Pb2+, Zn2+ and Al3+ are all white.
Ag+ is yellow
Cu+ is blue-green

Question 19

solubility of lead (Pb2+) salts

Answer 19

all insoluble except for the nitrate

all white except for lead iodide, which is yellow

Question 20

solubility of ammonium salts

Answer 20

all soluble

Question 21

solubility of chloride salts

Answer 21

all soluble except for AgCl - white, and PbCl2 - white

Question 22

solubility of bromide salts

Answer 22

all soluble except for AgBr - cream, and PbBr2 - white

Question 23

solubility of iodide salts

Answer 23

all soluble except for AgI - pale yellow, and PbI - bright yellow

Question 24

why is the delocalised structure of benzene preferred to the kekule model, in terms of reactions of benzene?

Answer 24

Benzene/A undergoes substitution (more easily than addition)

mention of delocalised electrons (in A) 
Benzene/A does not undergo addition (readily) 
because it has no double bonds/alkene 
OR B undergoes addition 
because it has double bonds/alkene 

Question 25

use ideas about reaction orders, RD steps and active sites to explain the shape of the rate-substrate concentration graph.

Answer 25

first part of graph first order for substrate – related to shape (e.g. ‘graph shows proportional’ / ‘linear’/ ‘rate doubles as conc. doubles’/ ‘constant positive gradient’ AW)  rds is equation 1 / substrate is in rds  second part of graph zero order for substrate  rds is equation 2 (or no longer equation 1) / substrate no longer in rds  all active sites (on enzyme) full/ saturated 