1997 - JAMB Chemistry Past Questions and Answers - page 1
1
35 cm3 of hydrogen was sparked with 12 cm3 of oxygen at 110°C and 760mm Hg to produce steam. What percentage of the total volume of gas left after the reaction is hydrogen?
A
11%
B
31%
C
35%
D
69%
correct option: b
Users' Answers & Comments2
2.85g of an oxide of copper gave 2.52g of copper on reduction and 1.90g of another oxide gave 1.52g of copper on reduction. The data above illustrates the law of?
A
constant composition
B
conservation of mass
C
reciprocal proportions
D
multiple proportions
correct option: d
Users' Answers & Comments3
An element, X, forms a volatile hydride XH3 with a vapour density of 17.0. The relative atomic mass of X is?
(H = 1)
(H = 1)
A
34.0
B
31.0
C
20.0
D
14.0
correct option: b
Molecular Mass = Vapour density x 2 = 17.0 x 2 = 34.0
∴ Relative Atomic Mass of X in XH3 = 34 - 3
= 31.0 ∴ x = 31.0
Users' Answers & Comments∴ Relative Atomic Mass of X in XH3 = 34 - 3
= 31.0 ∴ x = 31.0
4
A mixture of 0.20 mole of Ar, 0.20 mole of N2 and 0.30 mole of He exerts a total pressure of 2.1 atm. The partial pressure of He in the mixture is?
A
0.90 atm
B
0.80 atm
C
0.70 atm
D
0.60 atm
correct option: a
Total no mole = 0.2 + 0.2 + 0.3 = 0.7
Partial pressure of He = (0.3)/(0.7) x 2.1 =0.90
Users' Answers & CommentsPartial pressure of He = (0.3)/(0.7) x 2.1 =0.90
5
The temperature of a body decreases when drops of liquid placed on it evaporate because?
A
the atmospheric vapour pressure has a cooling effect on the body
B
a temperature gradient exists between the drops of liquid and the body causing the latter to vaporate
C
the heat of vapourization is drawn from the body causing it to cool
D
the random motion of the liquid molecules causes a cooling effect on the body
correct option: c
Users' Answers & Comments6
The electron configuration of two elements with similar chemical properties are represented by?
A
1s22s22p5 and 1s22s22p4
B
1s22s22p4 and 1s22s22p63s1
C
1s22s22p63s1 and 1s22s1
D
1s22s22p4 and 1s22s1
correct option: c
Users' Answers & Comments7
In the periodic table, what is the property that decreases along the periodic and increases down the group?
A
Atomic number
B
Electron affinity
C
Ionization potential
D
Atomic radius
correct option: d
Users' Answers & Comments8
Two elements, P and Q with atomic numbers 11 and 8 respectively , combine chemically to form the compound PxQY. The respective values of x and y are?
A
1 and 1
B
1 and 2
C
2 and 1
D
3 and 1
correct option: c
Users' Answers & Comments9
Oxygen is a mixture of two isotopes O and O with relative abundances of 90% and 10% respectively. The relative atomic mass of oxygen is?
A
16.0
B
16.2
C
17.0
D
18.0
correct option: b
816O, 818O
90% 10%
R.A.M = (90)/(100) x 16 + (10)/(100) x 18 = 14.4 + 1.8 = 16.2
Users' Answers & Comments90% 10%
R.A.M = (90)/(100) x 16 + (10)/(100) x 18 = 14.4 + 1.8 = 16.2
10
If 30cm3 of oxygen diffuses through porous plug in 7s, how long will it take 60 cm3 of chlorine to diffuse through the same plug?
A
12s
B
14s
C
21s
D
30s
correct option: c
(R)o/(R)a √(M)a/(MO (30/7)/(60/t) = √ (35.5)/(16)
(60/t) (30/7)/ √(35.5)/(16) t = (60/30)/(7) x (4)√35.5
t = (60 x 7 x √35.5)/(30 x 4) = 21s
Users' Answers & Comments(60/t) (30/7)/ √(35.5)/(16) t = (60/30)/(7) x (4)√35.5
t = (60 x 7 x √35.5)/(30 x 4) = 21s