1989 - WAEC Chemistry Past Questions and Answers - page 2
11
Which of the following gases will bleach moist litmus paper?
A
CI2
B
CO2
C
SO2
D
HCI2
correct option: a
Users' Answers & Comments12
Given that for the reaction KOH (aq) + HCI(aq) → KCI(aq) + H2O(L) H = - 54 Kj mol-1. What is the quantity of heat involved in the reaction?2NaOH(aq) + H2SO 4(aq) → Na2SO4(aq) + 2H 2O(l)?
A
- 108Kj
B
-54 kj
C
-27 kj
D
+27 kj
correct option: a
Given that \(KOH_{(aq)} + HCl_{(aq)} \to KCl_{(aq)} + H_{2}O_{(l)} ; \Delta H = -54 kJ/mol\)
The standard heat of neutralization is the amount of heat evolved when 1 mole of hydrogen ion from an acid reacts with 1 mole of hydroxide ion from the base to form one mole of water, under standard conditions.
\(\therefore 2NaOH_{(aq)} + H_{2}SO_{4(aq)} \to Na_{2}SO_{4(aq)} + 2H_{2}O_{(l)} ; \Delta H = -(2 \times 54 kjmol^{-1})\)
\(\therefore \Delta H = -108 kJmol^{-1}\)
13
When an element can exist in two or more forms in the same physical state, the element is said to exhibit
A
isotopy
B
isomerism
C
allotropy
D
hygroscopy
correct option: c
Users' Answers & Comments14
Which of the following carbohydrates does NOT usually occur in the crystalline form?
A
Fructose
B
Glucose
C
Sucrose
D
Maltose
correct option: e
Users' Answers & Comments15
Copper can best be purified by
A
roasting the impure copper in a blast furnace
B
heating the oxide with coke
C
electrolyzing a copper (ll) salt solution using the impure copper as the anode
D
converting the impure copper to a trioxonitrate (V)
correct option: c
Users' Answers & Comments16
Locally produced soap in which wood ash is used as the base is usually soft because the wood ash contains a lot of
A
sodium ions
B
potassium ions
C
lithium ions
D
calcium ions
correct option: b
Users' Answers & Comments17
Why is potassium fluoride added to the electrolyte in the extraction of sodium from fused sodium chloride?
A
Pure sodium chloride does not conduct electricity
B
Potassium fluoride prevents the sodium produced from attacking the electrodes
C
Potassium fluride increases conductivity
D
Potassium fluride reduces the temperature at which sodium chloride fuses
correct option: d
Users' Answers & Comments18
The rate of the hydrogen in the reaction Zn(s) + 2HCI (aq) → ZnCI 2(g) + H 2(aq) + H 2(g) can be increased by
A
using Zinc powder instead of Zinc granules
B
using dilute instead of concentrated hydrochloric acid
C
cooling the container in which the mixture is placed
D
using an alloy of zinc instead of pure zinc
correct option: a
Users' Answers & Comments19
Octane number is highest in petrol containing a high proportion of
A
heptane
B
octane
C
2-methylpentane
D
2, 4-dimethylpentane
correct option: e
Users' Answers & Comments20
Given the following half-cell reaction; 2Cl(aq) → CI2(g) + 2e, how many mole of electrons will be required to produce 1.12dm3 of chlorine gas at s.t.p? (Molar volume of a gas at s.t.p. = 22.4dm 3)
A
1.00
B
0.40
C
0.20
D
0.10
correct option: d
Users' Answers & Comments