1997 - WAEC Chemistry Past Questions and Answers - page 1
1
The phenomenon observed when dust particles collide randomly in a beam of sunlight is known as
A
Tyndal effect
B
diffusion
C
osmosis
D
brownian movement
correct option: a
Users' Answers & Comments2
The mass number of an element is the sum of its
A
electrons, neutrons and protons
B
electrons and protons
C
protons and neutrons
D
orbital electrons
correct option: c
Users' Answers & Comments3
How many unpaired electrons are there in an atom of an element with the following electronic configuration? 1s22s22p6
A
o
B
1
C
2
D
6
correct option: a
Users' Answers & Comments4
Radon is used as a tracer in medical research because it
A
is monatomic
B
is radioactive
C
is a noble gas
D
has a complete valence shell
correct option: b
Users' Answers & Comments5
What is the most probable group of an element which is a soft, silvery white solid and reacts violently with water?
A
Group 0
B
Group 1
C
Group 4
D
Group 6
correct option: b
Users' Answers & Comments6
In linear molecules, the bond angle is
A
90o
B
140o
C
109o
D
120o
correct option: e
Users' Answers & Comments7
A sodium atom and a sodium ion have the same
A
number of neutrons
B
number of electrons
C
electric charge
D
electronic structure
correct option: a
Users' Answers & Comments8
If the atomic number of an element X is 11 and that of nitrogen is 7, the most likely formula of the nitride of X is
A
X3N
B
XN3
C
X3N2
D
N2X
correct option: a
Users' Answers & Comments9
An increase in the pressure of a gas results in a decrease in its
A
mass
B
vapour density
C
volume
D
temperature
correct option: c
Users' Answers & Comments10
A given volume of methane diffuses in 20 seconds. How long will it take the same volume of sulphur (IV) oxide to diffuse under the same conditions? [CH4 = 16; SO2 = 64]
A
5 seconds
B
20 seconds
C
40 seconds
D
60 seconds
correct option: c
Applying the Graham's law defination; i.e,
\(\frac{R(SO_2)}{R(CH_4)} = \sqrt{\frac{M(CH_4)}{M(SO_2)}} = \frac{t(CH_4)}{t(SO_2)}\)
Where t(SO\(_2\)) = ?, M(SO\(_2\)) = 64
t(Ch\(_4\)) = 20 sec, M(Ch\(_4\)) = 16
therefore, \(\frac{t(SO_2)}{20}\) = \(\sqrt{\frac{64}{16}}\)
\(\frac{t(SO_2)}{20}\) = \(\frac{8}{4}\)
t(SO\(_2\)) = 8 x \(\frac{20}{4}\)
= 40 sec.