2022 Paper 2 Chemistry corrections Flashcards
What are the use of waste poly(alkenes)
- feedstock for cracking
- incineration to release energy
-make new materials by recycling
What is a diol?
Compound contains two hydroxyl (-OH) groups
Why would 2,2-dimethylpropane have a lower boiling point than its isomer pentane?
There are less London forces due to less points of contact
What is the difference between heterolytic bond fission and homolytic bond fission?
Homolytic fission occurs when the covalent bond breaks evenly, and each of the bonded atoms takes one of the shared pair of electrons from the bond. Each atom now has a single unpaired electron - called a radical.
Heterolytic fission: When the covalent bond breaks unevenly, and one of the bonded atoms takes both of the electrons from the bond.The atom that takes both electrons becomes a negative ion (anion).The atom that does not take the electrons becomes a positive ion (cation).
What is the classification of this dihalogenoalkane and why
Primary because both chlorine atoms are bonded to carbon atoms bonded to only one other carbon atom
Give a reason as to why nitrogen gas and not air is used in packet of crisps
Prevents oxidation of crisps
- Remember that air contains roughly 20% oxygen and so it is not unusual for oxidation to be a result when chemicals are exposed to the air.
Why does a nitrogen molecule have six shared electrons
Each electron pair is one bond
Nitrogen has three bonds between its atoms (triple bond)
Explain why ammonia molecule and the ammonium ion have different shapes and bond angles
Ammonia has a lone pair of electrons which repels more than bonded pairs of electrons
- Ammonia has three bond pairs of electrons and one lone pair
- Ammonia is trigonal pyramidal
Ammonium ion is tetrahedral
- Ammonia bond angle is 107
- Ammonium ion is 109.5
Butylamine, C4H9NH2 , reacts with ethanoyl chloride.
2C4H9NH2 + CH3COCl → C4H9NHCOCH3 + C4H9NH3+Cl–
Explain how this equation illustrates that butylamine acts as a nucleophile and as a base.
Amine group attacks as a nucleophile by attacking the C+ of the acyl chloride to produce hydrogen chloride.
It is also a base because the amine group reacts with acid/protons to produce C4H9NH3+Cl-.
What is ethanoyl chloride
An acyl chloride
What is butylamine
A typical amine
Ethanoyl chloride reacts with cold conc. solution of ethy
Ethanoyl chloride reacts with cold conc. solution of ethylamine. Mixture of N-ethylethanamide ( an N-substituted amide) and ethylammonium chloride
What happens If hydrogen chloride and ethylamine react
If hydrogen chloride and ethylamine react: ethylammonium chloride is formed
Describe the first stage of reaction between ethylamine and ethanol chloride
First stage involves a nucleophilic attack on fairly positive carbon atom by lone pair in the nitrogen atom in ethylamine
Describe the second stage of reaction between ethaylamine and ethanol chloride
Second stage is elimination stage which happens in two steps
First the carbon-oxygen double bond reforms and a chloride ion is pushed off
What are carbonyl group, aldehyde group and ketone group
Describe the difference between reflux and distillation apparatus
- Reflux is a technique
used in chemical
laboratories to dissolve
components that are hard
to be dissolved - Distillation is the action
of purifying a liquid by
the process of heating
and cooling - Reflux Purpose is to dissolve
components in a reaction
mixture that are hard to be
dissolved and to complete
to chemical reaction - Distillation Purpose is to separate
different components in
a mixture - Reflux Apparatus is composed of
a round-bottomed flask, a
condenser. a water bath
and heat source - Distillation Apparatus is composed of
a round-bottomed flask
connected to a Y adapter
which is connected to a
condenser attached to a
receiving flask
How can you make amines
from nitriles or halogenoalkanes
How do you make propylamine from reduction
Reducing nitriles via LiAl4 in dry ether
or
The reduction of nitriles using hydrogen and a metal catalyst (Pd catalyst)
What are the equations of reducing nitriles to make propylamine
With LiAl4 in dry ether:
CH3CH2CN + 4[H] → CH3CH2CH2NH2
With hydrogen and Pd catalyst:
CH3CH2CN + 2H2 → CH3CH2CH2NH2
Give the reagent and essential conditions for the formation of propylamine from a halogenoalkane.
- ethanolic/alcoholic
ammonia - heat and under pressure
Compare and contrast the structures, optical activity and reactions with acids and bases of alanine and glycine.
Include diagrams, structures and equations to illustrate your answer.
Similarities
They are both zwitterions:
NH3+CH(CH3)COO− / NH3+CH2COO−
Reaction with acid:
H+ + NH3+CH2COO− → NH3+CH2COOH or
H+ + NH3+CH(CH3)COO− → H3N+CH(CH3)COOH
Reaction with a base:
OH−+NH3+CH2COO−→NH2CH2COO−+H2O or OH−+NH3+CH(CH3)COO−→NH2CH(CH3)COO−+H2O
alanine has a chiral centre/ asymmetric
carbon atom/ non-superimposable mirror images
and
glycine does not
- (an aqueous solution of) alanine rotates the
plane (of polarisation) of plane-polarised
(monochromatic) light but glycine does not
Explain the difference in the volumes of 0.010 mol dm–3 hydrochloric acid required to completely react with separate 10.0 cm3 samples of aqueous lysine and of aqueous serine, both of concentration 0.010 mol dm–3.
- lysine requires twice (the volume of HCl) (1)
- (because) lysine has two (basic) amine/NH2 groups whereas serine has one
how do you make an ester
carboxylic acid and alcohol w conc. H2SO4 catalyst
or acyl chloride and alcohol:
If you add an acyl chloride to an alcohol, you get a vigorous (even violent) reaction at room temperature producing an ester and clouds of steamy acidic fumes of hydrogen chloride.
) Esters can be hydrolysed by heating under reflux with aqueous acid or alkali. Compare and contrast these two methods of hydrolysis for amyl acetate.
(similarity)
* both make the (same) alcohol / pentan-1-ol (1)
(differences)
* acid hydrolysis is reversible, alkaline hydrolysis is
irreversible (1)
* acid hydrolysis produces the carboxylic acid/ ethanoic acid and
alkaline hydrolysis produces the carboxylate / ethanoate (ion) (1)
* the acid is a catalyst and the alkali is a reactant
