Page 34 - PRE-U STPM CHEMISTRY TERM 1

Chemistry Term 1 STPM

ANSWERS

Chapter 1 Atoms, Molecules and Quick Check 1.5
Stoichiometry 1 (a) 714.15 g (b) 28.88 g (c) 3369.8 g
2 (a) 23.46 g (b) 8.56 g (c) 1.15 g
Quick Check 1.1 4 25
222 3 (a) 5.56  10 (b) 3.34  10
1 (a) Rn
86 Quick Check 1.6
(b) 234 Pa
91 1 (a) CaCO + 2HCl → CaCl + H O + CO 2
2
2
3
(c) 38 Ca (b) 2.00 g
20 (c) 80.0%
(d) 212 Pb
82 2 2
(e) 208 Tl; 208 Pb 3 1.95 mol dm –3
81 82
2 228 Y STPM Practice 1
90 Objective Questions
Quick Check 1.2 1 D 2 C 3 C 4 B 5 B
1 39.985 6 A 7 C 8 B 9 C 10 C
2 (a) 1.083 times 11 D 12 B 13 D 14 D 15 C
13
(b) 12 C : C = 9.9 : 0.1 16 A 17 B 18 D 19 D 20 B
3 12.0038 21 B 22 B 23 C 24 B 25 D
26 B 27 D 28 D 29 C 30 B
Quick Check 1.3 31 D 32 A
1 110.32 Structured and Essay Questions
2 (a) 3
(b) 206 M; 207 M; 208 M 1 (a) Number of protons in the nucleus of an atom.
(b) Total number of protons and neutrons in the
82
82
82
2+
(c) It is caused by M ion nucleus of an atom.
206
3 (a) (c) Atoms of the same element but with different
nucleon number.
2 Refer to section isotopes.
30.4 69.9
20 21 22
3 (a) Mole ratio N : O = 14 : 16
(b) 20.18
(c) 1.68 times = 2.1 : 4.4
= 1 : 2
Quick Check 1.4 Empirical formula is NO
1 (b) The molecular peak = 92 2
(NO )n = 92
2
46n = 92
n = 2
Molecular formula is N O
158 160 162 2 4
+
(c) m/e (46) = [NO ] or [N O ] 2+
Ratio: 158 : 160 : 162 = 1 : 2 : 1 m/e (94) = [N O O] + 2 4
2
16
18
2 (a) 3 : 2 (b) 12
4 (a) Refer to text
3 [Not to scale]
(b) Refer to text
(c) (i)
29.8
14 18 28 32
1.5
4 1.0
28 29 30 m/e
14 16 18 30 32 46 48 50 (28  29.8) + (29  1.5) + (30  1.0)
(ii) A =
r (29.8 + 1.5 + 1.0)
14 16 18 30 32 46 48 50
= 28.11
16
16
16
18
16
18
18
N + 16 O + 16 O + N O + N O + N O O + N O O + N O O + 28.11
2 (iii) = 2.34 times
12
357
12 Answers.indd 357 3/26/18 4:06 PM