A-LEVEL AP1 PAPER 2 MS

1.   (a)     k = rate / [A]2 or 
1
= 1.87 or 1.9
Answer scores 2
1.90 scores first mark only (incorrect rounding)
1
mol−1dm3s−1
Any order and independent of calculation
1
(b)     Expt 2 rate = 1.167 × 10−4 − 1.2 × 10−4 (mol dm−3 s−1)
If answers in table are not those given here, check their value of k in part (a) or use of alternative k.
1
Expt 3 [A] = 9.7 × 10−3 − 9.8(1) × 10−3 (mol dm−3)
If their k is incorrect in part (a) mark this part consequentially e.g. if k = 7.9 × 10−3 due to lack of squaring in (a)
Using alternative value for k
expt 2 4.9 × 10−7
Expt 2 rate = 1.4(4) × 10−4 (mol dm−3 s−1)
expt 3 1.5 ×10−1
Expt 3 [A] = 8.85 × 10−3 (mol dm−3)
(expt 2 6.24 × 10−5 × their k)
(expt 3 0.0134 / √k)
1
(c)     Slow step or rds involves only A
OR
B does not appear in the slow step or the rds
OR
B only appears after the slow step or the rds
Not B has no effect on the rate or B is not in the rate equation
Allow “it” for B
1
[6]

2.      (a)     propyl methanoate;
HCOOC3H7 + OH– → HCOO– + C3H7OH
1
OR
HCOOC3H7 + NaOH → HCOONa + C3H7OH;
1
(b)     order wrt A = 1;
1
order wrt NaOH = 1;
1
Initial rate in Exp 4 = 2.4 × 10–3;
1

(c)     (i)      r(ate) = k[A]
OR
r(ate) = k[A][NaOH]0;
(penalise missing [ ] but mark on)
(penalise missing [ ] once per paper)
(if wrong order, allow only units mark conseq on their rate eqs)
(penalise ka or kw etc)
1
(ii)     ;
1
= 0.45;
1
         s–1;
l
(iii)     (large) excess of OH– or [OH–] is large/high;
1
[OH–] is (effectively) constant
OR
[A] is the limiting factor                (Q of L mark)
1
 [11]
 
3.	(a)     (i)  
 
Mark is for insertion of numbers into a correctly rearranged rate equ , k = etc.
If upside down, score only units mark from their k
AE (−1) for copying numbers wrongly or swapping two numbers
1
= 1.8(3)
1
mol−2 dm+6 s−1
Any order
If k calculation wrong, allow units consequential to their k = expression
1
(ii)     5.67 × 10−4 (mol dm−3 s−1)   OR    their k × 3.1 × 10−4
Allow 5.57 × 10−4 to 5.7 × 10−4
1
(b)     (i)      2 or second or [D]2
1
(ii)     0 or zero or [E]0
1

(c)     (i)      Step 1 or equation as shown
Penalise Step 2 but mark on
1
(ii)
Ignore correct partial charges, penalise full / incorrect partial charges
If Step 2 given above, can score the mark here for

allow: OH− (must show lp)
If SN2 mechanism shown then no mark (penalise involvement of :OH− in step 1)
Ignore anything after correct step 1
1
[8]

4.     (a)     (i)      An appropriate alkene; CH3CH2CHCH2 or (CH3)2CCH2
1
Isomer 1
1
Isomer 2
1
Position isomerism
1
Mechanism
electrophilic attack and electron shift to Br (Unless H+ used)
1
carbocation
1
reaction with carbocation
[Allow mechanism marks for the alkene CH3CHCHCH3]
[Allow one mark if mechanism for minor product given]
1
(ii)     An appropriate carbonyl; CH3CH2CHO
1
Mechanism nucleophilic attack and electron shift to O
1
anion intermediate
1
reaction with anion
[Allow mechanism marks for the carbonyl (CH3)2CO]
1
         Isomer 1
1
Isomer 2
1
Optical isomerism
NB     Isomer structures must be tetrahedral
NB     Penalise “stick” structures once in part (a)
1

(b)     QoL
Large charge on carbonyl carbon atom due to bonding
to O and Cl
1
Nucleophiles have electron pairs which can be donated
1
Equation Species
1
Balanced
1
[18]
 
5.      (a)     dimethylamine
1
(b)     nucleophilic substitution
1

4
(c)     quaternary ammonium salt
1
(cationic) surfactant / bactericide / detergent / fabric softener or
conditioner/hair conditioner
1
(d)     

(allow CH3COOH or CH3COO– NH4+)
2
[10]

6.     (a)     (i)      Moles NaOH = mv/1000 = 1.50 × 72.5/1000 = 0.108 to 0.11 (1)
Moles of ethanoic acid at equilibrium = moles sodium hydroxide (1)
Moles ester = moles water (=moles acid reacted) (1)
 = 0.200 – 0.108 = 0.090 to 0.092 (1)
Moles ethanol = 0.110 – 0.091 = 0.018 to 0.020 (1)
KC      = [Ester] [Water]/[Acid] [Alcohol] (1)
Allow if used correctly
          = (0.091)2/0.109 × 0.019 = 3.7 to 4.9 (1)
Ignore units
NB     Allow the answer 4 one mark as correct knowledge
7
(ii)     Similar (types) of bond broken and made (1)
Same number of the bonds broken and made (1)
any number if equal
NB  If a list given then the total number of each type of bond broken and made must be the same
2
(b)     (i)      (Weak) dipole-dipole attraction between HCl molecules (1)
(Strong) hydrogen bonds between CH3COOH molecules (1)
NB     Ignore van der Waals forces
2
(ii)     Ethanoic anhydride is
cheap compared to ethanoyl chloride (1)
less corrosive than ethanoyl chloride or HCl evolved (1)
reaction less violent or vigorous or exothermic or dangerous
or safer to use (1)
less vulnerable to hydrolysis (1)
reaction more easily controlled (1)
Max 2
[13]
 
7.   (a)     Yes, because it is oxidised to ethanal / CH3CHO
OR it is oxidised to a compound that contains CH3CO group
Ignore ‘primary alcohols are oxidised to aldehydes’.
Need ‘yes’ and an explanation to be awarded the mark.
1
(b)     Mr CHI3 = 393.7 (M1)
Allow if clearly shown in a calculation.
Allow 394
1
Moles CHI3 = 10 / 393.7 = 2.54 × 10−2 (M2)
Allow a consequential answer on an incorrect Mr.
2.54 × 10−2 scores M1 and M2.
1
Moles I2 = 7.62 × 10−2 (M3)
Allow 3 × M2.
1
Mass I2 = 7.62 × 10−2 × 253.8 = 19.34g (M4)
Allow M3 × 253.8 or M3 × 254
1
Scaling 19.34 / 0.832 = 23.2g (M5)
Allow M4 / 0.832
Lose this mark if the answer is not given to 3 significant figures.
Answer without working scores M5 only.
Allow any chemically correct alternative method.
Calculations which combine several steps in one expression can score the marks for all of these individual steps.
1
(c)     Remove soluble impurities
Allow ‘remove excess sodium hydroxide / iodine’.
Allow ‘remove excess sodium methanoate / sodium iodide’.
Allow ‘remove excess reagents’.
1
(d)     Will not dissolve solid / solid is insoluble in water
Allow ‘will not react with solid’.
1
[8]

8.    (a)     Mg  +  2C6H4(OH)COOH  →  (C6H4(OH)COO)2Mg  +  H2
Accept multiples, including fractions.
1
(b)     Gas syringe / inverted burette over water / measuring cylinder over water
Collection apparatus must show graduations or be clearly labelled (eg syringe, burette, measuring cylinder).
1
[2]

9.	Identification of acid by suitable method eg named indicator, named carbonate, specified reactive metal
Ignore any reference to the smell of the ester.
1
with expected results
Do not allow the use of any instrumental method eg i.r. or n.m.r.; must be a chemical test.
1
Identification of alcohol by suitable method eg oxidation by acidified potassium dichromate(VI)
1
with expected results
1
[4]