Page 35 - PRE-U STPM CHEMISTRY TERM 1

Chemistry Term 1 STPM

5 (a) Negative. [Positive particles are attracted towards the P Cl Cl + 103
35
37
negative plate]
37
37
+
(b) H . It is lighter and hence deflected more. P Cl Cl + 105
m P Cl Cl Cl + 136
35
35
35
+
2
(c) (i) of H = 2
e +
35
35
37
1 P Cl Cl Cl 138
∴ Angle =  4° = 2°
2 P Cl Cl Cl + 140
37
37
35
(ii) Zero. Neutron is neutral and is not deflected. P Cl Cl Cl + 142
37
37
37
79
79
35
6 C H Br Br Cl : 220 ≡ (1  1  3) = 3 (c) 66 : 68 = 3 : 1
2 3
35
81
79
C H Br Br Cl : 222 ≡ 2(1  1  3) = 6 103 : 105 : 107 = (3  3) : 2(3  1) : (1  1)
2 3
81
35
81
C H Br Br Cl : 224 ≡ (1  1  3) = 3 = 9 : 6 : 1
2 3
79
79
37
C H Br Br Cl : 222 ≡ (1  1  1) = 1 138 : 140 : 142 : 144
2 3 = (3  3  3) : 3(3  3 1) : 3(3  1  1) : (1  1  1)
79
37
81
C H Br Br Cl : 224 ≡ 2(1  1  1) = 2 = 27 : 27 : 9 : 1
2
3
81
81
37
C H Br Br Cl : 226 ≡ (1  1  1) = 1 12 (a) Due to the presence of isotopes.
2
3
Relative abundance: 220 : 222 : 224 : 226 (b) Let the % abundance of X = a%
35
= (3 + 1) : (6 + 1) : (3 + 2) : 1 % abundance of X = 100 – a%
37
= 4 : 7 : 5 : 1 35.5 = 35a + 37(100 – a)
7 (a) Isotope with unstable nucleus and undergoes a = 75% 100
spontaneous disintegration to form nucleus of (c)
smaller isotopes. 75%
(b) (i) 227 W and 227 X
88 89 25%
4 0
(ii) A ≡ 4 He + e (4 α-particles and 1 β-particle)
2 –1
4 0 35 37
B ≡ He + 2 e
–1
2
(iii) They are isotopes.
13 (a) Relative molecular mass of Y = 12 × 9.5
8 (a) The amount of substance that contains the same = 114
number of particles as the number of atoms in 12 g Let the molecular formula of Y be C H 2n+2 .
n
of C. 12n + 2n + 2 = 114
12
(b) (i) 180 g n = 8
4.8 × 10 –3 Alkane Y is C H .
23
(ii) 180  (6.02  10 ) 25 8 18
19
= 1.61  10 molecules (b) C H + 2 O → 8CO + 9H O
2
2
18
2
8
89.5 25
(iii) Mass =  2.5 g = 2.24 g Volume of O required = × 0.15 dm 3
100 2 2
9 (a) Atoms having the same number of protons and the = 1.88 dm 3
same number of electrons, but different number of 100
neutrons. ∴ Volume of air needed = 20 × 1.88
(b) (i) 35 36 37 38 = 9.40 dm 3
1
35 CI + 35 CI H + 37 CI + 37 CI H +
1
Chapter 2 Electronic Structure of
(ii) 35 Cl H 2+ Atom
1
The energy required to form ion of +2 charge is
much higher. Quick Check 2.1
–1
10 (a) 18 34 60 1 (a) 602 kJ mol
15
(b) 1.51  10 Hz
16
H O CH OH CH COOH
18
2 3 3 –7
(c) 1.99  10 m
(b) CH —C— O— CH 2 (a) 3.0  10 m
18
–16
3 3
|| (b) 6.63  10 J
–10
O (c) 3.99  10 kJ mol –1
11
11 (a), (b) Species m/e value Quick Check 2.2
14
35
P Cl + 66 1 (a) 4.57  10 Hz (b) Visible
–1
14
2 (a) 5.08  10 Hz (b) 202.9 kJ mol
37
P Cl + 68
14
15
3 x = 3.20  10 Hz. y = 2.33  10 Hz
P Cl Cl + 101
35
35
358
12 Answers.indd 358 3/26/18 4:06 PM