1993 - WAEC Chemistry Past Questions and Answers - page 2
11
In which of the following changes is ∆S negative ?
A
H2O(l) → H2O(s)
B
C(s) + 1/2O2,/sub>(g) → CO(g)
C
PCI5(g) → PCl3(g) + Cl2(g)
D
NaCl(s) + aq →Na+ (aq) + Cl- (aq)
correct option: a
Users' Answers & Comments12
Chlorine is is used in water treatment as
A
a germicide
B
a decolorizing agent
C
an antioxidant
D
a coagulating agent
correct option: a
Users' Answers & Comments13
Which of the following pieces of deposited if a current of 10A was passed through a solution of copper(ll) salt for 965 seconds? (1F = 96500 C)
A
0.005 mole
B
0.025 mole
C
0.05 mole
D
1.00 mole
correct option: c
Users' Answers & Comments14
Some precious stones such as ruby and sapphire consist of aluminum oxide coloured by traces of the oxides of
A
group lV elements
B
group l metals
C
transition metals
D
alkaline earths
correct option: c
Users' Answers & Comments15
Consider the reaction represented by the following equation CaCI2 (aq) + H 2C2O 4(aq) ⇌ CaC 2O4(s) + 2HCI(aq). Which of the following would dissolve the precipitate of CaC 2O4 formed?
A
Stirring the mixture vigorously
B
Adding more calcium chloride solution
C
lncreasing the concentration of the ethanedioic acid
D
Adding concentrated hydrochloric acid
correct option: d
Users' Answers & Comments16
The following gases decolorize bromine water except
A
C2H6
B
C2H4
C
C2H2
D
C3H4
correct option: a
Users' Answers & Comments17
What volume of distilled water should be added to 400cm3 of 2.0 mole dm-3 \(H_{2}SO_{4}\) to obtain 0.20 mole dm-3 of solution>
A
600cm-3
B
800cm-3
C
1,000cm-3
D
3,600cm-3
correct option: d
\(400cm^{3} \to 2moldm^{-3}\)
\(0.4 dm^{3} \to 2moldm^{-3}\)
Multiplying in order to get the moles of the acid.
\(0.4dm^{3} \times 2moldm^{-3} = 0.8moles\)
After diluting to \(0.2moldm^{-3}\), the new volume will be
\(\frac{0.8}{0.2} = 4dm^{3}\)
Converting back to cm^3,
We have \(4 \times 1000cm^{3} = 4000cm^{3}\)
Hence, the volume of water added = \((4000 - 400)cm^{3} = 3600cm^{3}\)
18
Which of the following indicates the correct increasing order of oxidizing power of the halogens?
A
F < CI < Br < l
B
l < Br < CI < F
C
I < CI < Br < F
D
Br < I < CI < F
correct option: b
Users' Answers & Comments19
Which of the following substances is a peroxide?
A
Na2O2
B
CuO
C
PbO4
D
Fe2O
correct option: a
Users' Answers & Comments20
The component of air that removed when air is bubbled into alkaline pyrogallol solution is
A
carbon(lV) oxide
B
oxgyen
C
water vapour
D
nitrogen
correct option: b
Users' Answers & Comments