2004 - JAMB Chemistry Past Questions and Answers - page 2
11
The property of chlorine which causes hydrogen chloride to be more ionic than the chlorine molecules is its
A
electrovalency
B
electron affinity
C
electropositivity
D
electronegativity
correct option: d
Users' Answers & Comments12
Chlorine consisting of two isotopes of mass number 35 and 37 in the ratio 3:1 has an atomic mass of 35.5. Calculate the relative abundance of the isotopes of mass number 37
A
20
B
25
C
60
D
75
correct option: b
Let the relative abundance of oxygen with mass 37 be x%
∴ The relative abundance of the isotope of mass 35 = (100 - x)%. Total mass of isotopes of mass 37 = 37x, while that of 35 = 35(100 - x)
∴ Total mass of the 100 atoms
= 37x + 35(100 - x) = 35.5
= 37x + 3500 - 35x = 35.5
∴ Mean mass of chlorine atom = (2x + 3500)/100 = 35.5
2x + 3500 = 3550; x = 50/2 = 25
Users' Answers & Comments∴ The relative abundance of the isotope of mass 35 = (100 - x)%. Total mass of isotopes of mass 37 = 37x, while that of 35 = 35(100 - x)
∴ Total mass of the 100 atoms
= 37x + 35(100 - x) = 35.5
= 37x + 3500 - 35x = 35.5
∴ Mean mass of chlorine atom = (2x + 3500)/100 = 35.5
2x + 3500 = 3550; x = 50/2 = 25
13
Which of the following mixture of gases is likely to burn in flame
A
neon and hydrogen
B
nitrogen and helium
C
helium and neon
D
neon and nitrogen
correct option: a
Users' Answers & Comments14
Hardness of water is caused by the presence of ions of
A
magnesium and silver
B
cacium and magnesium
C
sodium and potassium
D
calcium and sodium
correct option: b
Users' Answers & Comments15
Pollution of underground water by metal ions is very likely in the soil that has high
A
acidity
B
alkalinity
C
chloride content
D
nitrate content
correct option: b
Users' Answers & Comments16
A carcinogenic substance is
A
asbestos dust
B
sawdust
C
nitrogen (II) oxide
D
carbon (II) oxide
correct option: a
Users' Answers & Comments17
The solubility in mol dm/-3 of 20g of CuSO4 dissolved in 100g of water at 180o is
[Cu = 64, S = 32, O =16]
[Cu = 64, S = 32, O =16]
A
0.13
B
0.25
C
1.25
D
2.00
correct option: c
Relative molecular mass of CuSO4 = 64 + 32 + 16 * 4 = 160
The number of moles of CUSO4 = reacting mass/molecular mass = 20/180 = 0.125
100g of water dissolved 0.125m of CuSO4
100g of water will dissolve (0.125 * 1000)/100 = 1.25mol dm3
Users' Answers & CommentsThe number of moles of CUSO4 = reacting mass/molecular mass = 20/180 = 0.125
100g of water dissolved 0.125m of CuSO4
100g of water will dissolve (0.125 * 1000)/100 = 1.25mol dm3
18
Calcium tetraoxosulphate (VI) dissolves in water only sparingly to form a
A
solution
B
suspension
C
precipitate
D
colloid
correct option: c
Users' Answers & Comments19
Which of the following compound is a normal salt?
A
NaHS
B
NaHSO4
C
NaHCO3
D
Na2CO3
correct option: d
Users' Answers & Comments20
What volume of 0.5 mol dm-3 H2SO4 will exactly neutralize 20cm3 of 0.1 mol dm-3 NaOH solution?
A
2.0 cm3
B
5.0 cm3
C
6.8 cm3
D
8.3 cm3
correct option: a
2NaOH + H2SO4 → Na2SO4 + 2H2O
CaVa/CbVb = ratio of acid/ratio of base
(0.5 * Va)/(0.1 * 20) = 1/2
∴ Va = 2.0cm
Users' Answers & CommentsCaVa/CbVb = ratio of acid/ratio of base
(0.5 * Va)/(0.1 * 20) = 1/2
∴ Va = 2.0cm