Page 38 - PRE-U STPM CHEMISTRY TERM 1

Chemistry Term 1 STPM
(b) (g) 4 (a) (b)

O O
x x x •• xx x x • x x O • x •
• • x • x •
O • N • x O •
x • • x • N N
– x x – • x
O • S • O O x • O • O x •
xx x x x • x • • •
O O
•• x x xx
Quick Check 3.2
(c) (h) 1 Pyramidal 8 Linear
••
xx xx 2 Linear 9 Square planar
3 Tetrahedral 10 Bent
x x x • x
x I I I – x • C x • O x
x • x x • xx 4 Trigon bipyramidal 11 Square-based pyramidal
5 Octahedral 12 Bent
xx •• •• xx 6 Tetrahedral 13 Trigon planar
7 Pyramidal 14 Bent
(d) (i)
–
O Quick Check 3.3
x • xx xx
1 Nitrogen is more electronegative than phosphorous. The
x x x bonding electrons in NH are closer to one another and
– x x – Cl S S Cl 3
O • P • O • • • experience greater repulsion.
x • • x xx xx 2 H S. Sulphur is more electronegative than Se.
2
O
Quick Check 3.4
(e) (j) 1 Polar 4 Non-polar
2 Polar 5 Non-polar
Cl
3 Non-polar 6 Non-polar
x •
Quick Check 3.5
x + x
Cl • P • Cl
x x • Chromium can make use of the electrons from the 3d as well
H • C x • N • as 4s sub-shell to form metallic bonds. Calcium can only make
x • x • •
use of electrons from the 4s sub-shell to form metallic bonds.
Cl
Quick Check 3.6
2 (a) (b) 1 H  O  CH  Cl 2
2
2
4
Number of electrons in the molecules increases.
Cl
Cl Cl Cl 2 Size of the molecules as well as the total number of
x • • x • x
x • • • electrons in the molecules increases from CH to SnH . As
4
4
a result, the van der Waals forces get stronger.
Cl x • Al x • Cl Al Al
x • x •
• • • x 3 (a) Relative Total Boiling
Cl Cl Cl Compound molecular number of point/°C
mass electrons
Silane 32.1 18 –112
3 (a)
Hydrogen 33.1 18 –61
Cl x Be x Cl sulphide
• •
(b) H S is polar but SiH is non-polar.
2 4
(b) Presence of empty orbitals in beryllium and lone-pair 4 CH CN. CH CN is polar but C H is non-polar.
3
3
3
8
electrons in the ammonia molecule. Quick Check 3.7
(c) (a) and (d)
H Cl H
x • • x • Quick Check 3.8
x x x x 1 (a), (b), (d), (e) and (f)
H • N x Be x N • H
2 Ethanol: Strong hydrogen bonding
x • • x • Dimethyl ether: Weak van der Waals forces
H Cl H
3 HCOOH can form more intermolecular hydrogen
bonding compared to ethanol.
361
12 Answers.indd 361 3/26/18 4:06 PM