Chemistry mark scheme

Question 1

The rate equation for a reaction is
rate = k[E]
Explain qualitatively why raising the temperature by 10 °C has a much greater
effect on the rate of the reaction than doubling the concentration of E.
[3 marks]

Answer 1

Reaction occurs when molecules have E≥Ea
Raising T by 10 °C causes many more molecules to have this E
Whereas doubling [E] only doubles the number with this

Question 2

Alcohol A (CH3)2CHCH(OH)CH3 undergoes reactions separately with acidified
potassium dichromate(VI) and with concentrated sulfuric acid.
Deduce the IUPAC name for alcohol A. (1)

Answer 2

3-methylbutan-2-ol

Question 3

Butanone is reduced in a two-step reaction using NaBH4 followed by
dilute hydrochloric acid.
Write an overall equation for the reduction of butanone using [H] to represent
By considering the mechanism of the reaction, explain why the product has
no effect on plane polarised light.esent the
reductant. (6)

Answer 3

Indicative Chemistry content
Stage 1: Formation of product
* Nucleophilic attack
* Planar carbonyl group
* H– attacks from either side (stated or drawn)
Stage 2: Nature of product
* Product of step 1 shown
* This exists in two chiral forms (stated or
drawn)
* Equal amounts of each enantiomer/racemic
mixture formed
Stage 3: Optical activity
* Optical isomers/enantiomers rotate the plane
of polarised light equally in opposite directions
* With a racemic/equal mixture the effects
cancel

Question 4

Name the mechanism when H-Br reacts but-1-ene

Answer 4

Electrophilic addition