A-LEVEL PAPER 3 PP10 MS

1.    (a)    Yellow / purple (solution)
Allow orange / brown (solution)
1
Brown precipitate / solid
1
[Fe(H2O)6]3+ + 3OH− → Fe(H2O)3(OH)3 + 3H2O
1
(b)     Blue (solution)
Allow pale blue
1
Dark / deep blue solution
Ignore any reference to blue ppt
1
[Cu(H2O)6]2+  + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 4H2O
Can be in two equations
1
(c)     Colourless (solution)
1
White precipitate / solid
Do not allow grey
1
Bubbles / effervescence / gas evolved / given off
Do not allow just CO2
1
2[Al(H2O)6]3+ + 3CO32− → 2Al(H2O)3(OH)3 + 3CO2 + 3H2O
1
[10]

2.   (a)     As concentration increases the amount of heat given out increases / temperature increases (M1)
Any order.
Ignore references to an exothermic reaction.
1
More successful collisions or reactions in a given time OR more particles have the activation energy (M2)
Allow could be a second / nth order reaction.
1
(An increase in temperature or more heat given out) increases the rate of a reaction (M3)
1
(b)     The magnesium is coated with an oxide / MgO (M1)
Allow magnesium hydroxide.
1
MgO / the coating / the corrosion product has to be removed before Mg will react
OR Mg and MgO / the coating / the corrosion product react at different rates
OR Initially MgO / the coating / the corrosion product reacts not Mg (M2)
Ignore inert coating.
1
(c)     Any two from:
Any order.
Slower with hot water or faster with steam
The hot water produces Mg(OH)2 / the hydroxide OR steam produces MgO / the oxide
(Slow) bubbling with hot water OR bright white light / flame / white solid with steam
2 max

(d)     Magnesium sulfate is soluble and calcium sulfate is insoluble / slightly soluble / magnesium sulfate is more soluble / calcium sulfate is less soluble / correct trend in solubility (M1)
Any order.
M1 requires a comparison of the two solubilities.
Calcium sulfate coats the surface of the calcium (M2)
Coating prevents further contact with / reaction by the acid (M3)
‘Calcium sulfate forms a protective coating’ scores M2 only.
3
[10]

3.     (a)     Order with respect to iodine: 0 (1)
Overall order: 2 (1)
2
(b)     Rate constant: k =  = 4.4(4) × 10–4 (1)
Units: mol–1 dm3 s–1 (1)
3
(c)     Appears in rate equation (1)
OR implied by mention of concentration or order
          does not appear in (stoichiometric / overall) equation (1)
2
(d)     pH = –log10 [H+] (1)
      = 1.25
[H+] = 0.056(2) (1)
           rate = (4.44 × 10–4) × (1.50) × (0.0562)
 = 3.75 × 10–5 (1) (mol dm3 s–1)
(3.7 — 3.8)
Can score all 3 conseq on k from part (b)
3
[10]
 
4.      (a)     2Ca5F(PO4)3+ 9SiO2 +15C9CaSiO3 + CaF2 +15CO + 6P
1
(b)     M1 (P4 =) 0
M2 (H3PO4 =) (+) 5
Accept Roman numeral V for M2
2
(c)     H2SO4
Both numbers required
Mr      = 2(1.00794) + 32.06550 + 4(15.99491)
= 98.06102 or 98.0610 or 98.061 or 98.06 or 98.1
Calculations not required
and
H3PO4
Mr      = 3(1.00794) + 30.97376 + 4(15.99491)
= 97.97722 or 97.9772 or 97.977 or 97.98 or 98.0
1

(d)     (i)      A substance that speeds up a reaction OR alters / increases the rate of a
reaction AND is chemically unchanged at the end / not used up.
Both ideas needed
Ignore reference to activation energy or alternative route.
1
(ii)     The addition of water (QoL ) to a molecule / compound
QoL- for the underlined words
1
(iii)     M1 CH3CH=CH2 + H2O  CH3CH(OH)CH3
            (C3H6)
For M1 insist on correct structure for the alcohol but credit correct equations using either C3H6 or double bond not given.
M2 propan-2-ol
2
[8]
 
5.      (a)    A shared electron pair or a covalent bond (1)
Both electrons from one atom (1)
OR when a Lewis base reacts with a Lewis acid
Mark points separately
2
(b)     Brønsted-Lowry acid: A proton or H+ donor (1)
Not H3O+
1
(c)     Two atoms or two points of attachment (1)
Each donating a lone electron pair (1)
OR forms 2 (1) co-ordinate bonds (1)
OR donates two (1) pairs of electrons (1)
2
(d)     Change in co-ordination number: 6 to 4 (1)
          Reason for change: chloride ligands are larger than water ligands (1)
2
OR greater repulsion between chloride ligands
DO NOT allow chlorine or Cl
(e)     Same number (1), and same type of bonds (1), broken and made
2
(f)      ClNH3CH2CH2NH3Cl (1)
OR (NH3CH2CH2NH3)2+ 2Cl–
Allow C2H10N2Cl2 and NH3ClCH2CH2NH3Cl
1
[10]

6.   (a)     (i)      CH3CH(OH)COOH + NaOH → CH3CH(OH)COONa + H2O
OR CH3CH(OH)COOH + OH− → CH3CH(OH)COO− + H2O
Not ambiguous mol formulae for product - must show COONa or CO2Na or COO− or CO2−
1
(ii)     [H+] = Ka OR pH = pKa
1
pH = 3.86
Allow more than 2 decimal places but not fewer.
1
(iii)    M1 buffer
Ignore acidic but penalise alkaline or basic.
1
Any two out of the three marks M2 , M3 & M4
M2  Large lactate concentration in buffer
      OR sodium lactate completely ionised
M3  added acid reacts with / is removed by lactate ion or A− or sodium
       lactate or salt
       OR equation H+ + A− → HA
Ignore reaction of H+ with OH−
Ignore reference to equilibrium unless it is shown.
M4  ratio [HA] / [A−] stays almost constant
Ignore H+ or pH remains constant.
Max 2

(b)    (i)      
No marks if ester link missing
Correct ester link
allow –COO–
NB Correct answer scores 2
Ignore n here (compare with (d)(iv).
Ignore brackets
1
OR

All rest correct with trailing bonds
If OH or COOH on either or both ends, lose one, ie dimer scores 1
If more than two repeating units, lose 1
1
(ii)     (Poly)ester ie allow ester
Not terylene.
Ignore spaces and brackets in answer.
1
(iii)    

Allow any cyclic C6H8O4
1
(iv)    

Penalise n here (compare with (d)(i)
Ignore brackets.
Not allow Ph for phenyl.
1
(v)     In landfill, no air or UV, to assist decay
OR not enough water or moisture (to hydrolyse polyester)
Allow landfill has / contains:
no or few bacteria / micro-organisms / enzymes compared with compost heap
OR less oxygen
OR lower temperature.
1
[12]

7.	D
[1]
8.	B
[1]
9.	D
[1]
10.	B
[1]
11.	C
[1]
12.	A
[1]
13.	D
[1]
14.	D
[1]
15.	A
[1]
16.	D
[1]
17.	B
[1]
18.	C
[1]
19.	C
[1]
20.	D
[1]
21.	A
[1]
22.	D
[1]
23.	D
[1]
24.	D
[1]
25.	D
[1]
26.	D
[1]
27.	D
[1]
28.	D
[1]
29.	B
[1]
30.	C
[1]
31.	C
[1]
32.	B
[1]
33.	A
[1]
34.	C
[1]
35.	D
[1]
36.	D
[1]