NCEA Level 3 Chemistry 91391 (3.5) — page 1 of 8
SAMPLE ASSESSMENT SCHEDULE
Chemistry 91391 (3.5): Demonstrate understanding of the properties of organic compounds
Assessment Criteria
Achievement
Demonstrate understanding involves naming using
IUPAC conventions (no more than eight carbons in the
longest chain), drawing structural formulae of organic
compounds, and giving an account of their physical
properties and / or reactivity. This requires the use of
chemistry vocabulary, symbols, and conventions.
Achievement with Merit
Achievement with Excellence
Demonstrate in-depth understanding involves making
and explaining links between structure, functional
groups, physical properties, and reactivity of organic
compounds. This requires explanations that use
chemistry vocabulary, symbols, and conventions.
Demonstrate comprehensive understanding involves
elaborating, justifying, relating, evaluating or
comparing and contrasting the links between the
structure, functional groups, physical properties and /
or reactivity of organic compounds. This requires the
consistent use of chemistry vocabulary, symbols,
and conventions.
Evidence Statement
One
Expected coverage
Ethanoyl chloride
(a)
Achievement
Merit
TWO names correct.
2–chlorobutanoic acid
1-amino -methylpropane
3-D structure drawn, eg
ONE isomer drawn correctly
with 3D arrangements of
groups around chiral carbon
OR
(b) (i)
H2N
in (b) (i), the isomers drawn
are mirror images but an
error in the way the groups
are connected to chiral
carbon.
Correct 3D arrangements
drawn, which are mirror
images
Excellence
NCEA Level 3 Chemistry 91391 (3.5) — page 2 of 8
Structures of P and Q drawn, eg:
Structure of P or Q drawn.
NH2
O
CH C CH3
OH
Explanation of chiral carbon
linked to structure of P.
OH O
NH2 C C H
CH3
(b) (ii)
OH O
NH2 CH2 CH CH
P has a chiral carbon, which contains a carbon with four different
groups attached.
ONE dipeptide drawn
correctly
OR
O
(c) (i)
C N
H
peptide link
(c) (ii)
Dipeptides contain the CO–NH (peptide /amide) linkage. This
forms when the amine group of one molecule reacts with the
carboxylic acid group of the other molecule. Two dipeptides are
possible as either the COOH from glycine can react with the NH2
from serine, or the NH2 from glycine can react with the COOH
from serine.
An explanation of the TWO
dipeptides formed, linked to
the structures of the amino
acids.
NCEA Level 3 Chemistry 91391 (3.5) — page 3 of 8
The amide link is hydrolysed in both acid and basic conditions.
In acid conditions the product is:
(d)
ONE product of hydrolysis
drawn. (Products drawn but
does not recognize salt
formation.)
Product of hydrolysis drawn
with acid OR base, with
limited reasons.
The acid will form a salt with the amine group, NH 2.
In basic conditions the product is:
Not Achieved
NØ
No response; no relevant evidence.
N1
Candidate provides some accurate statements without answering any question completely.
N2
Candidate provides any ONE statement for Achievement.
A3
Candidate provides any TWO statements for Achievement.
A4
Candidate provides any THREE statements for Achievement.
M5
Candidate provides any ONE statement for Merit.
M6
Candidate provides BOTH statements for Merit.
E7
Candidate provides statement for Excellence AND ONE Merit statement.
E8
Candidate provides statement for Excellence AND TWO Merit statements.
Achievement
Merit
Excellence
Structures of BOTH
hydrolysis products are
justified in terms of the
reaction of the molecule with
acid and with base.
NCEA Level 3 Chemistry 91391 (3.5) — page 4 of 8
Two
(a)
Expected coverage
Achievement
Reagant: Alcoholic KOH.
KOH (alcoholic) used
Reaction and reason: This is an elimination reaction as a
hydrogen atom and a chlorine atom on adjacent carbon atoms
are removed, forming a carbon-to-carbon double bond.
OR
Dilute solutions of Cr2O72-/H+ (or MnO4-/H+)
Observation of ONE
reaction with chosen
reactant (out of TWO
possible reactions given)
reason for elimination
reaction given.
OR
will not react.
(b) (i)
CH3– CH2– CH2 –OH will react with Cr2O72-/H+ and will turn from
orange to green (or MnO4-/H+ will turn from purple to colourless).
The product formed is:
Add water
will not react.
(b) (ii)
reacts vigorously with an exothermic reaction.
The product formed is CH3– COOH.
Merit
two correct reagents (allow
oxidation to aldehyde).
ONE pair of compounds
distinguished (with chosen
reactant and observations
for BOTH compounds) with
product.
Excellence
NCEA Level 3 Chemistry 91391 (3.5) — page 5 of 8
O
W
CH3 CH CH2OH
Y
CH3
CH3 CH C Cl
CH3
CH3 CH C OH
CH3
OR
O H
O
X
Z
CH3 CH C NCH 3
CH3
Compound W
This compound is oxidised by Cr2O72-/H+ to an acid so it has to
be a primary alcohol (or an aldehyde – rejected as too many H
atoms). The OH has to be on an end C. It’s a branched chain
molecule so there is a CH3 on the 2nd C atom.
Hence:
(c)
Compound X
This is formed when
is oxidised to an acid.
Hence:
Compound Y
The functional groups of
TWO out of FOUR
compounds given
one reason for a functional
group given.
TWO correct structures with
reasons given. (Error in W
may be carried through for
these two structures.)
Structures correct with
justification for the functional
groups and reactions given.
NCEA Level 3 Chemistry 91391 (3.5) — page 6 of 8
A substitution reaction occurs with SOCl2; the OH in:
is replaced with Cl.
Hence:
Compound Z
A substitution reaction occurs with CH3NH2; the Cl is replaced
with CH3NH2.
Hence:
O H
CH3 CH C N CH 3
CH3
Not Achieved
NØ
No response; no relevant evidence.
N1
Candidate provides some accurate statements without answering any question completely.
N2
Candidate provides any ONE statement for Achievement.
A3
Candidate provides any TWO statements for Achievement.
A4
Candidate provides any THREE statements for Achievement.
M5
Candidate provides any ONE statement for Merit.
M6
Candidate provides BOTH statements for Merit.
E7
Minor errors (eg omission or inaccuracies) from the Excellence criteria.
E8
Candidate provides ALL the evidence from the Excellence criteria.
Achievement
Merit
Excellence
NCEA Level 3 Chemistry 91391 (3.5) — page 7 of 8
Three
Expected coverage
Achievement
Merit
Excellence
TWO products correct.
(a)
CH3– CH2– CO– CH3 with Cr2O72-/ H+
TWO products correct.
No reaction occurs.
CH3– CH2– CO– CH3 with NaBH4
(b)
Product is CH3– CH2– CHOH– CH3
CH3– CH2– CHOH– CH3 with concentrated H2SO4
Products are CH3– CH2– CH= CH2 (minor) and
CH3– CH= CH– CH3 (major)
(c)
Butanal /aldehydes can be oxidised using Cr2O72-/
H+ (Reactant 1) to form a carboxylic acid, butanoic
acid. However, butanone/ketones cannot be
oxidised.
Both butanal/aldehydes and butanone/ketones can
be reduced using NaBH4 (Reactant 2) to form
ONE similarity OR ONE
difference identified.
ONE similarity AND ONE
difference explained in terms of
the structures or functional
groups.
Reaction scheme of butanal and
butanone shows both similarities
with NaBH4 and differences with
both Cr2O72-/ H+ and
concentrated H2SO4 including
major and minor products.
NCEA Level 3 Chemistry 91391 (3.5) — page 8 of 8
alcohols. Aldehydes form primary alcohols and
ketones form secondary alcohols.
With concentrated H2SO4 alcohols form alkenes.
The primary alcohol CH3– CH2– CH2 – CH2OH forms
only one product as the H and OH atoms on
adjacent carbon atoms are replaced with a carbonto-carbon double bond.
The secondary alcohol CH3– CH2– CHOH– CH3
forms a mixture of products as OH is on the 2nd
carbon atom. Either the 1st H is removed, forming
CH3– CH2– CH= CH2 (minor) or the 3rd H is
removed, forming CH3– CH= CH– CH3 (major).
Not Achieved
NØ
No response; no relevant evidence.
N1
Candidate provides some accurate statements without answering any question completely.
N2
Candidate provides any ONE statement for Achievement.
A3
Candidate provides any TWO statements for Achievement.
A4
Candidate provides any THREE statements for Achievement.
M5
Candidate provides ONE similarity OR ONE difference, explained in terms of the structures/functional groups.
M6
Candidate provides ONE similarity AND ONE difference, explained in terms of the structures/functional groups.
E7
Minor errors (eg omission or inaccuracies) from the Excellence criteria.
E8
Candidate provides ALL the evidence from the Excellence criteria.
Achievement
Merit
Excellence