GCE
Chemistry B (Salters)
Unit F331: Chemistry for Life
Advanced Subsidiary GCE
Mark Scheme for June 2014
Oxford Cambridge and RSA Examinations
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This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which marks were awarded by examiners. It does not indicate the details of the discussions which took place at an examiners’ meeting before marking commenced. All examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes should be read in conjunction with the published question papers and the report on the examination.
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© OCR 2014
F331
1.
Mark Scheme
These are the annotations, (including abbreviations), including those used in scoris, which are used when marking
Annotation
Meaning
Blank Page – this annotation must be used on all blank pages within an answer booklet (structured or unstructured) and on each page of an additional object where there is no candidate response.
Benefit of doubt
Contradiction
Cross
Error carried forward
Ignore
Not answered question
Benefit of doubt not given
Not good enough
Rounding error
Repeat
Noted but no credit given
Error in no. of significant figures
Tick
Omission mark
2.
June 2014
Subject-specific Marking Instructions that apply across the whole question paper to be included here.
Please tick the place where a candidate scores a mark on every question.
1
F331
Mark Scheme
Question
1
(a)
Answer
Process: fractional distillation
Property: boiling point /condensation point
(b) (i)
H H H
H C C C H
H H H
June 2014
Marks Guidance
1
both required for 1 mark
IGNORE references to length of hydrocarbon chain number of carbons/mass/volatility
Watch for CONS eg ‘boiling pt and melting pt’
}
}
1
H
C C C H
H H
H
H
NOT lower case ‘h’
(ii)
(c)
IGNORE bond angles and any other formulae
unsaturated
1
(i)
C 10 H 22
1
(ii)
catalyst in different state/phase to reactants adsorption (on to surface)
C 2 H 4 + C 8 H 18
ALLOW minor spelling errors
2
2
(iii)
IGNORE “products”
QWC: adsorption must be spelt correctly for second mark adsorbed etc to be allowed
IGNORE “engine autoignite”
tendency of fuel to autoignite/pre-ignite/knock/pink
ALLOW ‘better mileage’/better performance
IGNORE ‘less knocking’ AW
IGNORE incomplete combustion
more efficient/stops possible damage
(iv) wedge going in front (of plane of paper) and dotted line behind AW
1
must have both
ALLOW (atoms) coming out, going behind linked to wedges and dots
(v)
1
DO NOT ALLOW ‘H’ alone
hydrogen/H 2
2
F331
Mark Scheme
Question
(d) (i)
Answer different structural formulae for the same molecular formula
(ii)
June 2013
Marks Guidance
1
ALLOW same molecular formula different arrangement/order of atoms/different structure (AW)
ALLOW same number and type of atoms for molecular formula NOT ‘same chemical/physical properties’
IGNORE references to functional groups
2
OR
OR
OR
Three correct full structural formulae scores max of 1 mark three correct isomers score both marks two correct one mark
1
(e)
2
DO NOT ALLOW condensed formulae e.g. CH 3
IGNORE bond angles
ALLOW one mark for all correct skeletal structure
2 marks if completely correct
1 mark for correct two double bonds
Total
3
15
F331
Mark Scheme
Question
2 (a)
(b)
Answer
2SO 2 (g) + 2H 2 O(g or l) + O 2 (g) correct species and balance states June 2013
Marks
2
2H 2 SO 4 (aq)
Guidance
ALLOW ‘half’ or multiples
DO NOT ALLOW (l) for sulfuric acid
ALLOW ‘state’ mark if species correct but equation unbalanced 1
(c)
ALLOW alkaline instead of basic
And answers like..
“it is an acid/base reaction and the acidic sulfur dioxide is neutralised by the CaO”
4
CaO/it is basic
IGNORE references to bonding pairs
carbon dioxide has two sets/groups of electrons/areas of electron density
Watch for CON “three bonding groups in SO 2 ”
sulfur dioxide has three sets etc.
Watch out for CON – “repel as far apart as possible” for one species, but “don’t repel ……..”for the other
electrons repel as far as possible/minimise repulsion
IGNORE ‘repel as much as possible’ IGNORE ‘push’
NOT ‘atoms repel’
IGNORE ‘bonds repel’
ALLOW for ‘electrons’: ‘these’ (if 1st mpt scored) or any of the terms allowed for the first mpt
NO ecf (eg 4areas/109)
(three groups gives) 1200 (allow 115 -1250)
(d)
(e)
2
advantage – no CO 2 /CO/NOx/particulates
ALLOW working or answer for 1st marking pt.
199.7/200 on answer line scores both marks
2
100 ÷ 32.1 (3.112 or 3.125 if 32 used) answer to first marking point x 64.1 (64) and correctly evaluated (=199.7or 200.31)
NOT ‘less’ CO 2 /CO/NOx/particulates.
IGNORE references to abundance/availability of either fuel/greenhouse gases must have idea waste is radioactive
disadvantage – (disposal of) radioactive waste
4
F331
Question
(f)
Mark Scheme
Answer
June 2013
Marks
2
Guidance
IGNORE ‘covalent’ in right-hand column
carbon: covalent; giant /network
IGNORE ‘lattice/molecular/molecules’ in top right box
sulfur: covalent; (simple) molecular/ small molecules
ALLOW id-id for sulfur in bottom left box
ALLOW ‘simple molecule’ in bottom right box
Total
5
13
F331
Mark Scheme
Question
3
(a)
Answer
Nu
mb er of prot ons
Num ber of neutr ons
5
5
5
Boro n-11 5
6
Marks Guidance
1
All correct for the mark
Num ber of electr ons
Boro n-10 (b)
Isot ope June 2013
5
(i)
(percentage)abundance/amount/intensity (of the isotopes)
1
ALLOW ‘their %’s in a sample of boron’ AW
ALLOW answers which say there is more boron-11 ora
ALLOW relative (isotopic) abundance
IGNORE ‘abundance of peaks’
IGNORE references to masses
(ii)
Mass of each isotope multiplied by abundance/peak height/frequency/amount/intensity/value
2
ALLOW sum of isotopic mass x % abundance (scores both marks)
ALLOW sum divided by total abundance for 2nd mpt
ALLOW ÷ 100 (y axis not labelled)
2nd mark depends on first being scored
(calculate) average/mean
(iii) (accelerated to) same KE heavy/heavier ions: move slower
OR reach detector later/last
3
IGNORE ‘atoms’ for 1st mpt
DO NOT ALLOW reference to negative ions for 2nd mark
AW
any reference to KE made up of mass and velocity terms or KE = ½mv2
6
ALLOW ‘Heavier ions are accelerated less’ ORA for 3rd mp. F331
Mark Scheme
Question
(c) (i)
Answer
June 2013
Marks Guidance
2
Large/small swapped scores 1 mark if all else correct
Ionising radiation beta Property
Relative mass
Relative charge
Deflection by electrical field Stopped by a minimum of 4
+2
0
-1
small
large
paper
Al foil
one for each column
(ii)
3
(c)
2
1
+
(iii) lack of penetration AW
(d)
F
F
B
ALLOW ideas of stopped by container/Al foil/clothing etc
ALLOW “don’t travel far”
For covalent structure
IGNORE bond angles
Only one electron symbol used maximum 1
A lone pair appearing on B CONs 2nd mark
ALLOW correct ionic dot-and-cross with 1 mark for correct B structure including charge and 1 for 3 correct fluorides including charges (see below)
F shared electrons
ALLOW
ALLOW ecf for 2nd nucleon after wrong numbers on He
MAX one mark if any number on right e.g Li7 3
DO NOT ALLOW He on top of arrow
DO NOT ALLOW charges on He/Li
2
+
lone pairs
7
F331
Mark Scheme
Question
Answer
June 2013
Marks Guidance
ALLOW 2 electrons on B for ionic structure
(e)
(i)
(ii)
Time taken for half the radioactive nuclei to decay OR mass to decrease by half OR radioactivity to reduce by a half OR time taken for count rate / amount to drop by half
(mass)ratio of U-235 to lead/parent to daughter or vice-versa
1
Must mention time/how long for something to reduce by half: nuclei, atoms, substance, isotope(s), radioactivity, mass
NOT nucleus, “a nuclei”, atom (ie in singular)
DO NOT ALLOW ‘decompose’ for ‘decay’
2
First mark for idea that both lead and uranium need measuring Mark separately
an indication of time/age being related to number of half-lives elapsed (iii) Age of material small compared to half life (AW)
OR answer that links unreliability/inaccuracy of measurement with so little decay (AW)
1
(iv) light nuclei/atoms (of elements) [must be plural] fuse/join to give heavier nucleus/nuclei/element(s)/atom(s)
1
proportion/amount/ratio of lead to uranium gives indication of age of material/rock/mineral (ora) scores 2
IGNORE ‘half-life too long’ (in stem)
Either ‘light’ or ‘heavy’ must be mentioned but not necessarily both. E.g. “two light nuclei join to give a new nucleus” scores.
IGNORE ‘small nuclei’ OR ‘large nuclei’ ie small light nuclei join to form large heavy(ier) nucleus scores
But “two light nuclei fuse” alone does not score
Total
8
19
F331
Mark Scheme
Question
4 (a) (i)
(ii)
June 2013
Marks Guidance
1
ALLOW 1670/1700
IGNORE sign
Answer
1672J
3
moles of sodium bicarbonate (= 12 / 84) = 0.143 or 1/7
ALLOW either working or evaluation for 1st mark
2nd mark is for evaluation
ALLOW ecf from 4a(i) and from moles bicarbonate
enthalpy change per mole 1672 ÷ 0.143 (or 1672 x 7) =
11700 or 11.7 (ignore units)
11700 or 11.7 or ecf from 4a(i) gains first two marking pts
3rd marking point is for sig fig, sign and expressing answer to 2nd mp in kJ
+12
+12 on answer line scores all three marks
12 scores 2; -12 scores 2 (and max 1 for any other negative number from ecf)
+12000, 12000 or -12000 scores two
(iii) energy/heat transfer between the surroundings and the solution 1
NOT ‘heat loss’
ALLOW ‘heat gain from surroundings’
ALLOW ‘calorimeter’ for ‘surroundings’
ALLOW non-standard conditions AW
ALLOW ‘specific heat is only approximate’ AW
(iv) moles of CO 2 = 12/84 OR 0.143 OR 1/7 OR answer to 1st mp of 4a(ii)
2
3.4(3 etc) scores both marks
72 scores 0
10.285/10.29/10.3 scores 1 overall
vol = 3.4(3) OR ‘answer to 1st mp of 4a(ii) x 24’ evaluated
vol = answer to 1st mp of 4a(ii) x 3 x 24 evaluated scores
1 mark overall
2nd mark - ALLOW ecf only from incorrect Mr of NaHCO 3
9
F331
Mark Scheme
Question
(b)
June 2013
Marks Guidance
2
Both needed to score first mark
Answer bond breaking endothermic AND bond making exothermic 2nd mark must describe an endothermic process
NOT ‘more bonds broken than made’
NOT ‘energy needed to make bonds’ for 2nd mark
more energy taken in to break bonds than released when bonds form
OR value of endothermic processes larger (than the exothermic) ORA
(c)
4
a measure of the disorder/ways of arranging particles
ALLOW references to chaos/randomness of system
ALLOW ‘atoms’, ‘molecules’ for ‘particles’
IGNORE ‘ways of arranging a particle/molecule/ atom’
(singular)
IGNORE ‘ways of arranging atoms in a molecule’
entropy of gases>liquids>solids ora
ALLOW ‘gases have highest entropy, solids have lowest’
solid (and liquid) on LHS/reactants to gases (and liquids)on
RHS/products ora
ALLOW ‘more gases are formed’
More moles/molecules of product than reactant
ALLOW ‘more moles/molecules are formed OR greater amount of particles are formed’ but IGNORE “more moles/molecules of gases are formed” for this mark.
Total
10
13
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