,CHEMISTRY PAPER 2 OCR 2025 QUESTIONS AND CORRECTLY
WELLDEFINED ANSWERS LATEST ALREADY GRADED A+
(2025/2026)
What two types of bond are within an alkene? - CORRECT ANSWERS-sigma
and pi
sigma bond - CORRECT ANSWERS-the direct overlapping of two orbitals
pi bond - CORRECT ANSWERS-the sideways overlap of p orbitals
C=C how many pi bonds and sigma bonds are in this - CORRECT ANSWERS-
one sigma two pi bonds
what two types of isomers are found in alkenes - CORRECT
ANSWERS-cis/trans and E/Z
Difference between E/Z isomers and Cis/trans isomers - CORRECT ANSWERS-
E/Z compares relative position based in priority groups (IP rules) look at the
atomic number of the first bonded element
Cis/Trans compares the relative positions of identical groups
major and minor products in alkenes - CORRECT ANSWERS-the major
product forms the most stable carbocation intermediate during alkene reactions
tertiary>secondary>primary
,what type of polymer do alkenes produce? - CORRECT ANSWERS-addition
polymers
synthesis of an organic liquid - CORRECT ANSWERS-once reaction is complete
into a separating funnel. Neutralise any excess acid using sodium carbonate
(stops bubbling when all gone)
Allow 2 layers to settle
Use density into to establish layers. If density into not given, add water to
establish aqueous layer.
(aqueous layer get bigger)
Density of water is 1 anything greater is more dense.
collect the organic layer
add a drying agent to remove small traces of water left in the organic layer (e.g..
anhydrous CaCl2)
If the question tells you the boiling point of the organic liquid say distil dried
product and collect fraction that comes over the boiling point.
3 ways to determine purity of products - CORRECT ANSWERS-1. boiling point
should match known data, boils over a narrow range
or
2. Run TLC, measure Rf value, compare to known data values/Run TLC and
compare to chromatogram of pure sample
or
3. Run NMR/IR/Mass spectrum, compare to spectral database of pure
compounds.
, How to purify by recrystallisation? - CORRECT ANSWERS--dissolve in a
minimum volume of hot solvent
-cool in ice to recrystallise (impurities stay in solution)
-filter using Büchner flask/reduced pressure filtration
-wash with cold solvent
-dry
Does reflux have an open or closed system? - CORRECT ANSWERS-open
overall equation for ozone depletion - CORRECT ANSWERS-O3 + O -> 2O2
rate of formation of ozone = - CORRECT ANSWERS-rate of breakdown of
ozone by UV light =
what type of compound breaks down the ozone layer? - CORRECT ANSWERS-
chlorofluorocarbons
Initiation reaction of CCl3F
what is the mechanism, equation and why the radicals formed - CORRECT
ANSWERS-homolytic bond fission
Cl. + CCl2F.
C-Cl bond broken as its weaker than C-F
Evidence for the structure of delocalised benzene against the kekule structure -
CORRECT ANSWERS--Bond lengths of benzene are the same
-enthalpy of hydrogenation less exothermic than expected
WELLDEFINED ANSWERS LATEST ALREADY GRADED A+
(2025/2026)
What two types of bond are within an alkene? - CORRECT ANSWERS-sigma
and pi
sigma bond - CORRECT ANSWERS-the direct overlapping of two orbitals
pi bond - CORRECT ANSWERS-the sideways overlap of p orbitals
C=C how many pi bonds and sigma bonds are in this - CORRECT ANSWERS-
one sigma two pi bonds
what two types of isomers are found in alkenes - CORRECT
ANSWERS-cis/trans and E/Z
Difference between E/Z isomers and Cis/trans isomers - CORRECT ANSWERS-
E/Z compares relative position based in priority groups (IP rules) look at the
atomic number of the first bonded element
Cis/Trans compares the relative positions of identical groups
major and minor products in alkenes - CORRECT ANSWERS-the major
product forms the most stable carbocation intermediate during alkene reactions
tertiary>secondary>primary
,what type of polymer do alkenes produce? - CORRECT ANSWERS-addition
polymers
synthesis of an organic liquid - CORRECT ANSWERS-once reaction is complete
into a separating funnel. Neutralise any excess acid using sodium carbonate
(stops bubbling when all gone)
Allow 2 layers to settle
Use density into to establish layers. If density into not given, add water to
establish aqueous layer.
(aqueous layer get bigger)
Density of water is 1 anything greater is more dense.
collect the organic layer
add a drying agent to remove small traces of water left in the organic layer (e.g..
anhydrous CaCl2)
If the question tells you the boiling point of the organic liquid say distil dried
product and collect fraction that comes over the boiling point.
3 ways to determine purity of products - CORRECT ANSWERS-1. boiling point
should match known data, boils over a narrow range
or
2. Run TLC, measure Rf value, compare to known data values/Run TLC and
compare to chromatogram of pure sample
or
3. Run NMR/IR/Mass spectrum, compare to spectral database of pure
compounds.
, How to purify by recrystallisation? - CORRECT ANSWERS--dissolve in a
minimum volume of hot solvent
-cool in ice to recrystallise (impurities stay in solution)
-filter using Büchner flask/reduced pressure filtration
-wash with cold solvent
-dry
Does reflux have an open or closed system? - CORRECT ANSWERS-open
overall equation for ozone depletion - CORRECT ANSWERS-O3 + O -> 2O2
rate of formation of ozone = - CORRECT ANSWERS-rate of breakdown of
ozone by UV light =
what type of compound breaks down the ozone layer? - CORRECT ANSWERS-
chlorofluorocarbons
Initiation reaction of CCl3F
what is the mechanism, equation and why the radicals formed - CORRECT
ANSWERS-homolytic bond fission
Cl. + CCl2F.
C-Cl bond broken as its weaker than C-F
Evidence for the structure of delocalised benzene against the kekule structure -
CORRECT ANSWERS--Bond lengths of benzene are the same
-enthalpy of hydrogenation less exothermic than expected
