AS-LEVEL PAPER 1 PP9 MS

1.      (a)     Ability (or power) of an atom to attract electron density
(or electrons or ‑ve charge) (1)
in a covalent bond (1)
or shared pair
If remove an electron lose first mark
2
(b)     Trend: increases (1)
Explanation: nuclear charge (number of protons) increases (1)
electrons in same shell (1)
OR similar shielding
OR atoms similar size or smaller
OR 1 mol of e-
3
(c)     Heat / enthalpy / energy for removal of one electron (1)
from a gaseous atom (1)
can score in an equation
must have first mark to score the second
2
(d)     (i)      2 (1)
(ii)     Two elements (or Na / Mg) before the drop (in energy) to Al (1)
(iii)     ionisation energy of Al < that for Mg (1)
(iv)    fall in energy from P to S (1)
or discontinuity in trend
From Al to P there are 3 additional electrons (1)
or three elements
For second mark idea of block of 3 elements
5
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2.      (a)     (i)      100 ×10–3 × 0.500    =     5.00 × 10–2 (mol)
accept 5 ×10–2 / 0.05
1
(ii)     27.3 ×10–3× 0.600    =     1.64 × 10–2 / 1.638 × 10–2 (mol) only
1
(iii)     1.64 ×10–2 (mol)
Mark conseq on (ii)
1
(iv)    5.00 × 10–2   -   1.64 × 10–2   =   3.36 × 10–2 (mol)
Mark conseq on (i) & (iii)
1
(v)     3.36 × 10–2 × ½ = 1.68 × 10–2 (mol)
If 2.78 × 10–2 used 1.39 × 10–2
Mark conseq on (iv)
1
1.68 × 10–2 × 132(.1) or 1.39 × 10–2 × 132(.1)
Mark for Mr
1
= 2.22 g or 1.83 g
1

(b)     pV = nRT
1
 = 8.4(1) × 10–3 (mol)
1
 =  (1)
1
= 408.5 – 410.5 (K)
Mark conseq on moles
Note Sig. fig. penalty - apply once if single sf given, unless calc works exactly
1
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3.    (a)    Al + 1.5Cl 2 → AlCl3
Accept multiples.
Also 2Al + 3Cl2 → Al2Cl6
Ignore state symbols.
1
(b)      Coordinate / dative (covalent)
If wrong CE=0/2 if covalent mark on.
1
Electron pair on Cl − donated to Al(Cl 3)
QoL
Lone pair from Cl − not just Cl
Penalise wrong species.
1
(c)     Al2Cl6 or AlBr3
Allow Br3Al or Cl6Al2
Upper and lower case letters must be as shown.
Not 2AlCl3
1
(d)     SiCl4 / silicon tetrachloride
Accept silicon(4) chloride or silicon(IV) chloride.
Upper and lower case letters must be as shown.
Not silicon chloride.
1
(e)     
 
Accept shape containing 5 bonds and no lone pairs from Tl to each of 5 Br atoms.
Ignore charge.
1
Trigonal bipyramid(al)
1

(f)     (i)      Cl — Tl — Cl
Accept this linear structure only with no lone pair on Tl
1
(ii)     (Two) bonds (pairs of electrons) repel equally / (electrons in) the bonds repel to be as far apart as possible
Dependent on linear structure in (f)(i).
Do not allow electrons / electron pairs repel alone.
1
(g)     Second
1
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4.          Structure and hardness
M1
Q of L   both macromolecular/giant atomic/giant covalent/giant molecular;
1
M2
C atoms in diamond joined to 4 other C atoms / diagram with min 5 C
atoms i.e. shows tetrahedral shape / coordination number = 4;
1
M3
C atoms in graphite joined to 3 other C atoms diagram with clear
extended hexagonal plane/pattern i.e. shows trigonal planar shape /
coordination number = 3;
1
M4
diamond hard / crystal strong;
(not diamond stronger than graphite)
1
M5
because of 3-D structure / rigid structure / not layered;
1
M6
graphite (soft) as layer can slide over each other;
1
M7
Q of L   as only (weak) van der Waals’ forces between layers;
1
Melting point (for either allotrope)
M8
covalent bonds must be broken / overcome;
1
M9
which are strong / many / hard to break;
(M9 tied to M8)
1
          Other difference
M10
diamond is non-conductor of electricity, graphite is conductor
OR appropriate difference in appearance;
1
[9]

5.    (a)     Kc = 
 
Penalise ( ) in this part but can score units; mark on in (b)
If Kc expression wrong no marks in this part but can score M1 & M3 in (b)
1
units = mol−1 dm3
1
(b)     [O2] = or or
 
Correct answer scores three marks
Ignore ( ) in this part
Penalise contradiction in M1
M1
1
0.061(4)
If Kc expression wrong in (a) can score M1 here for rearrangement of their Kc & M3 for multiplication by 1.4
M2
mol O2 = 0.0614 × 1.4 = 0.086 (allow 0.085−0.087)
If Kc or rearrangement wrong here score only M3 for multiplication by 1.4
1
M3 = correct answer of (M2 × 1.4)
M3
1
(c)     (i)      No effect OR none OR no change OR stays the same
1
(ii)     Effect: Increase or more SO3
Increase or more SO3
If wrong effect, no further marks, but M2 and
M3 are independent of each other
M1
1
Fewer mole(cule)s on RHS
or 3 moles to 2 moles
or (eqm shifts) to side with fewer moles
(V3 or) residual V decreases in numerator of Kc expression
M2
1
Equilibrium moves / shifts to reduce the pressure /
oppose the increase in pressure
to keep Kc constant,
ratio 
must increase
Allow to oppose the change only if increase pressure mentioned
M3
1
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6.	Add (hydrochloric) acid to the mixture;
Allow correct acid eg nitric acid.
1
Filter to isolate strontium sulphate;
Do not allow ‘drain’ or decant’
1
[2]

7.    (a)     M1  Increases / gets bigger
If M1 is incorrect CE = 0 for the clip
If M1 is blank, mark on and seek to credit the correct information in the text
M2  requires a correct M1
M2 requires correct M1
More shells or sub-shells or (main) levels or sub-levels or orbitals (of electrons)
If “molecules” penalise M2
Not simply “more electrons”
Not “more outer shells”
Ignore reference to nuclear charge and shielding
2
(b)     (i)      Increases / gets more reactive / reacts more vigorously / violently (down the Group)
1
(ii)     Sr   +   2H2O         Sr(OH)2   +   H2
Credit multiples and correct ionic equations
Ignore state symbols
1
(c)     Ba(OH)2
This MUST be a formula so ignore the name
Credit Ba2+ 2OH−
Ignore state symbols
1
[5]

8.  (a)     Correct completion of table
(7.2 – 9.4 – 10.3 – 11.5 – 12.2 – 13.1)
Any error loses the mark.
1
Appropriate scales for axes
No penalty for missing labels but the graph must cover at least half of the available area.
1
All points plotted correctly
Allow ±1 small square.
1
Line of best fit acceptable
Must be a reasonably smooth curve but make allowance for freehand drawing passing within one small square of each point.
Do not penalise minor doubling of line.
1
(b)     Maximum mass at (44.0 / 4) = 11.0 g
giving a max. pressure of 1.7 ± 0.1 MPa
Allow this pressure range only.
Check that candidate’s answer matches graph.
1

(c)     7.2 g of NaCl in 250 cm3 represents 28.8 g dm–3
Allow 0.49 but not 0.5; otherwise do not penalise precision of answer
1
Molarity = 0.492 mol dm–3
Conseq. to their graph value for 100 kPa to 2 or 3 sig.
1
(d)     Measuring cylinder = (1 / 250) × 100 = 0.4%
Balance = (0.1 / 7.2) × 100 = 1.4%
Both values correct for the first mark.
Balance error conseq. on their 100 kPa mass value.
Ignore precision of answers.
1
Combined error 1.8%
When error being calculated is not stated, allow if the calculations are in the same order as in the question (measuring cylinder, balance).
If only combined error given then 1 mark only.
1
(e)     (i)      The points are good enough to be able to draw a smooth curve because the line passes through / close to all points.
Mark consequentially on candidate’s graph
1
(ii)     There are no anomalous points
Mark consequentially on candidate’s graph
1
(f)     The experiment only seeks an approximate figure for the maximum pressure
Allow words to that effect.
1
(g)    (i)      Toxic (to marine life)
Allow phrasing which implies a detrimental effect on marine ecology.
1
(ii)     Mixing the effluent with (sea) water to dilute it
Penalise any method which removes the salt or which implies storage.
1
(h)    2Br– + Cl2 → 2Cl– + Br2
Allow NaBr or KBr
1
(i)     The cost of removing water / heating would be too high
Discount answers based on toxicity or speed of reaction.
Allow answers based on cost of using sulfuric acid.
1
(j)     (i)      Carbon
Allow C, soot, graphite, coal.
1
(ii)     Formed by the decomposition of organic material / living organisms in the sea water
Allow ‘erosion of coal beds’.
1
(iii)    Dissolve the solid formed in water
Do not allow melting of the solid.
1
Filter off the insoluble particles
1
(k)    Ca(OH)2 + 2HCl → CaCl2 + 2H2O
Allow Ca(OH)2 + 2H+ → Ca2+ + 2H2O
Allow multiples.
1
(l)     In agriculture / to raise the pH of soil / (Lime-based) mortars in construction
Allow words to that effect.
1
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