June 2020 Paper 2

Question 1

Define the term overall order of reaction.

Answer 1

-The sum of powers

Question 2

Explain how the structural feature of an enzyme enables it to catalyse the hydrolysis of one isomer but not another isomer

Answer 2

-the enzyme has an active site
-the enzyme has a complementary shape to the isomer

Question 3

How can you tell that ethanoic anhydride has reacted with an alcohol

Answer 3

-a sweet smell is produced

Question 4

What is a hazard of using phosphoric acid

Answer 4

-it is corrosive

Question 5

How to calculate mass from volume and density

Answer 5

mass = volume x density

Question 6

Describe two important precautions when heating a mixture of ethanol and crude aspirin

Answer 6

-ethanol is flammable so use water bath
-heat to temp below boiling point

Question 7

Suggest two ways in which the melting point of crude aspirin would differ from the melting point of pure aspirin

Answer 7

-it would be lower
-the melting point would be over a range of values

Question 8

State why Si(CH3)4, CCl4 and CDCl3 are used in 1
H NMR spectroscopy.
Explain how their properties make them suitable for use in 1
H NMR spectroscopy.

Answer 8

-1a CDCl3 or CCl4 solvent
1b TMS as reference / calibration / standard / peak
at 0 (ppm)
1c Inert (so unlikely to react with the sample allow if
inert tied to either TMS or CDCl3 or CCl4)
Stage 2 CCl4 or CDCl3 as solvent:
2a (Both) have no H (atoms so give no signals in
spectrum) tied to either CDCl3 or CCl4
2b CCl4 non polar (- good solvent for non-polar
organic molecules)
2c CDCl3 polar covalent molecule (– good solvent
for polar organic compounds)
Stage 3 TMS as reference:
3a (Lots (12) of equivalent H to) give one signal /
single environment
3b Signal in an area away from other typical H
signals / peak upfield from others
OR
(Low electronegativity of Si shifts) signal right
3c Easy to remove / volatile / low bp