1990 - WAEC Chemistry Past Questions and Answers - page 2
11
How many molecules are there in 14g of nitrogen gas at s.t.p? (n = 14, Avogadro Number = 6. 0 x 1023 mol-1)
A
1.2 x 10 23
B
3.0 x 1023
C
6.0 x1023
D
1.2 x 1024
correct option: c
Users' Answers & Comments12
Which of the following correctly explains entropy?
A
the natural tendency for a system to achieve a greater disorder
B
a balance of two driving forces between free energy and enthalpy changes
C
the cause of spontaneity of a reaction
D
a measure of the enthalpy of a reaction
correct option: a
Users' Answers & Comments13
The gas that is liberated when iron is heated with concentrated tetraoxosulphate (VI)acid is
A
H2S
B
\(SO_{2}\)
C
HCI
D
SO3
correct option: b
2Fe (s) + 6H2SO4 (l) → Fe2(SO4)3 (aq) + 3SO2 (g) + 6H2O (l)
14
Which of the following salts in aqueous solution will have a pH greater than 7?
A
NaCl
B
ACI3
C
FeCI3
D
Na 2SO4
correct option: e
Users' Answers & Comments15
The compound of copper which is used in electroplating dyeing, printing, wood preservation and as a fungicide is
A
copper (ll) hydroxide
B
copper (ll) trioxonitrate (V) pentahydrate
C
copper (ll) tetraoxosulphate (VI) pentahydrate
D
copper (ll) oxide
correct option: c
Users' Answers & Comments16
What is the molecular formula of a compound whose empirical formula is CH2O and molar mass is 180? (H = 1, C = 12, O = 16)
A
C 4H 8O2
B
C 4H 8O3
C
C 6H 10O5
D
C 6H 12O6
correct option: d
Users' Answers & Comments17
MO and X 2O represent the formula of oxides of elements M and X respectively . If M and X should combine to form a separate compound, what would be the formula of the compound?
A
MX2
B
M2X
C
MX
D
M3X2
correct option: a
Users' Answers & Comments18
Which of the following pollutants is biodegradable ?
A
Sewage
B
Plastics
C
Metal scrape
D
Lead compounds
correct option: a
Users' Answers & Comments19
In the reaction represented by the equation; 2FeCI3 + SO2 + 2H2O → 2FeCL2 + H2SO4 + 2HCI the oxidation number of sulphur changes from
A
+2 to + 6
B
+ 4 to + 6
C
0 to + 6
D
- 2 to + 4
correct option: b
Users' Answers & Comments20
Which of the following equations represents the reaction leading to the removal of permanent hardness of water?
A
Ca(HCO 3)2 → CaCO3 + H2O + CO2
B
MgSO4 + Na 2CO3 + Na 2SO
C
Ca(OH) 2 + 2HCI → CaCI 2 + 2H 2O
D
Ca(HCO3)2 + Ca(OH)3 → 2CaCO3 + 2H2O
correct option: b
Users' Answers & Comments