Author: Luke Edwards-Stuart

Paddington Academy

TOPIC 3 HW MS

1.       (a)     Hydrogen/H bonds
Not just hydrogen
1
van der Waals/vdw/dipole-dipole/London/temporarily induced
dipole/dispersion forces
Not just dipole
1
(b)     

M1 for partial charges as indicated in diagram (correct minimum)
M2 for all four lone pairs
M3 for H bond from the lp to the H (δ+) on the other molecule
Lone pair on hydrogen CE = 0
OHO CE = 0
If only one molecule of water shown
CE = 0
3
(c)     Hydrogen bonds/IMF (in water) stronger
OR
IMF/VDW/dipole-dipole forces (in H_2S) are weaker
OR
H bonding is the strongest IMF
Ignore energy references
Comparison must be stated or implied
1

(d)     Atoms/molecules get larger/more shells/more electrons/more
surface area
Not heavier/greater Mr
1
therefore increased Van der Waals/IMF forces
Ignore references to dipole-dipole forces
1
(e)     Dative (covalent)/coordinate
If not dative/coordinate CE = 0/2
If covalent or blank read on
1
(Lone) pair/both electrons/two electrons on O(H_2) donated (to H^+)
OR pair/both electrons come from O(H_2)
Explanation of a coordinate bond specific to oxygen or water required
Not just H+ attracted to lone pair since that is nearer to a H bond
1
(f)      ionic
1
if not ionic CE = 0
oppositely charged ions/+ and – ions or particles
atoms or molecules loses M2 and M3
1
ions attract strongly OR strong/many (ionic) bonds must be broken
S^– loses M2
Reference to IMF loses M2 and M3
1
[13]
 2.     (a)     (i)      positive ions (1)
(attract) delocalised electrons (1) (or sea of or free or mobile) (1)
Confusion with ‑ve ions
or ionic lattice C.E. = 0
(ii)     more protons (1) (or Mg^2+ more charge than Na^+)
attracts delocalised (or bonding) electrons more strongly (1)
Delocalised: can be brought forward from (a) (i)
OR more delocalised electrons (1)
Attacks positive ions more (1)
Metallic bonding is stronger scores one mark, only given if
no other marks awarded
4
(b)     macromolecular (1) (or giant molecule etc)
covalent (1)
strong covalent bonds (1)
or bonds require much energy to break
3

(c)     delocalised (OR free or sea of or mobile) electrons (1)
1
(d)     Planes (1)
weak (bonds) forces between planes (1)
2
or v.dw forces between planes
[10]
 
3.          (a)     (i)      3 (bonding) pairs of electrons (1)
allow 3 bonds
         repel equally (1) (or as much as possible)
Or get as far apart as possible
(ii)     Predicted bond angle: 118° (allow 117 - 119°) (1)
Explanation: lone pair (1)
repels more than bonding pair (1)
Allow EXP if  < 118°
but C.E. = 0 if   120°
5
(b)     Name of shape: Tetrahedral (1)
Example: CH4 etc (1)
Allow correct ion
2
(c)     (i)      90° (1)
(ii)     lone pairs (or they) repel more than bonding pairs (or most) (1)
(so are) as far apart as possible (1)
Mark independently
(iii)     square planar (1)
allow square
4
(d)     
Penalise sticks (i.e. N‑) once but N must be shown
2
[13]

 

4.       (a)     Force 1: Van der Waals’ (1)
          Force 2: dipole - dipole (1)
          Force 3: hydrogen bonding (1)
OR London, Dispersion, temporary dipole
3
(b)     (i)      covalent between atoms (1)
OR within molecule
         Van der Waals’ between molecules (1) 
(ii)     molecular (1)
(iii)     Bonds (or forces) between molecules must be broken or loosened (1)
OR V.dW forces
OR intermolecular forces
Mention of ions CE=0
4
(c)     (i)      H-Bonding in HF (1)
         (dipole-) dipole in HCl (1)
OR V.dW
         H-bonding is stronger than dipole-dipole or V.dW (1)
OR H-bonding is a strongest intermolecular force for 3^rd mark
(ii)     HI bigger molecule than HCl (1)
OR Heavier, more e^’s, more electron shells, bigger M_r, more polarisable
         Therefore the forces between HI molecules are stronger (1)
QL mark (Look for unambiguous statements using correct terminology)
5
(d)     (i)      ionic (1)
Strong forces between ions (1)
OR lots of energy required to break bonds
(ii)     All bonds must be broken (1)
mention of molecules etc CE=0
3
(e)     macromolecular (1)
OR giant molecule / lattice or correct diagram
          Strong covalent bonds (1)
OR lots of energy required to break bonds
2
[17]
 
5.             (i)       Bonding in Na_2S: ionic (1)
	    Bonding in CS_2:  covalent (1)
ignore other words such as dative / polar / co-ordinate
(ii)     Clear indication of electron transfer from Na to S (1)
1 e^– from each (of 2) Na atoms or 2 e^– from 2 Na atoms (1)
QoL correct English
(iii)     

Correct covalent bonds (1)
All correct including lone pairs (1)
Allow all •s or all ×s
M2 tied to M1
NOT separate e^–s in S•- 2 l p
(iv)    CS_2 + 2H_2O → CO_2 + 2H_2S (1)
Ignore state symbols even if wrong
7
[7]
 
6.      (a)     (i)      Electronegativity (difference) or suitable description (1)
Accept F and Cl are highly electronegative
Not both atoms are highly electronegative
(ii)     HF = hydrogen bonding (1)
HCl = (permanent) dipole-dipole bonding or even van de Waals’ (1)
Hydrogen bonding stronger / is the strongest IMF (1)
Accept a statement that HF must have the stronger IMF, even if no IMFs identified
The explanation must be based on intermolecular forces/attractions
Note: if the explanation is clearly intramolecular = CE
4
(b)     Electron pair or lone pair donated (1)
Do not accept ‘donation of electrons’
          From chloride ion to Al or AlCl_3 (1)
M1 can be earned by a general explanation of coordinate bonding, even if the electron pair is said to come from Al. The second mark, M2, is for this specific bond
Ignore missing charge
2
(c)     
4
                 
PCl_5 shown as trigonal bipyramid    PCl_4^+ shown as tetrahedral
[Look for:  ONE solid linear Cl-P-Cl bond]        NO solid linear Cl-P-Cl bonds]
Bond Angle(s) 90° and 120° (1)                       Bond angle(s) 109 or 109.5° (1)
[10]
 
7.      (a)     dative / coordinate (covalent) bond;
1
Lone/non-bonding pair / both electrons;
1
(donated) from P to H^+;
1
(b)     

pyramidal OR trigonal pyramid 109()°;
(accept tetrahedral)
4
[7]

8.	C
[1]
9.	A
[1]
10.	D
[1]