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Chemistry
WAEC / WASSCE 2018
Nature of Matter & Separation Techniques
Solution
The process of extraction of iron from its ore is
A
decomposition
B
oxidation
C
reduction
D
sublimation
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The Iron is to to be gotten by the removal of oxygen from its ore, and this is called a reduction reaction.
Source: Myschool Past Questions Archive (Record #48963)
Chemistry
WAEC / WASSCE 2018
Water, Solutions & Solubility
Solution
What is the solubility of a salt if 0.4g of it is obtained on evaporating 200\(cm^{3}\) of its saturated solution to dryness?
A
0.08\(gdm^{-3}\)
B
2.00\(gdm^{-3}\)
C
8.00\(gdm^{-3}\)
D
80.00\(gdm^{-3}\)
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
1000\(cm^{3}\) = 1\(dm^{3}\)
200\(cm^{3}\) = 0.2\(dm^{3}\)
⇒ 0.2\(dm^{3}\) contains 0.4g
hence, solubility of the salt which is the amount of the salt dissolvable in 1\(dm^{3}\) is
\(\frac{0.4g}{0.2dm^{3}} = 2.0gdm^{-3}\)
Source: Myschool Past Questions Archive (Record #48965)
Chemistry
WAEC / WASSCE 2018
Acids, Bases, pH & Salts
Solution
An acidic salt has
A
double anions in its aqueous solution
B
a single cation in its aqueous solution
C
hydrogen ions in its aqueous solution
D
hydrogen atoms in its aqueous solution
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Acid salts are salts whose aqueous solutions are acidic in character, implying that their aqueous solutions possess hydrogen ions.
Source: Myschool Past Questions Archive (Record #48966)
Chemistry
WAEC / WASSCE 2018
Chemical Energetics & Thermochemistry
Solution
A reaction is endothermic if the
A
reaction vessel feels cool during the reaction
B
enthalpy change is negative
C
bond forming energy exceeds bond breaking energy
D
heat of formation of reactants exceeds heat of formation of products
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Endothermic reactions absorb heat from their surroundings during the reaction process. This means that in the course of the reaction the vessel being used in the reaction will be cool in the process.
Source: Myschool Past Questions Archive (Record #48967)
Chemistry
UTME / JAMB 2018
Water, Solutions & Solubility
Solution
A sample of hard water contains some calcium sulphate and calcium hydrogen carbonate. The total hardness may therefore be removed by
A
boiling the water
B
adding excess calcium hydroxide
C
adding a calculated amount of calcium hydroxide
D
adding sodium carbonate
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
its D because when sodium carbonate reacts with calcium hydrogentrioxocarbonate it gives sodium hydrogentrioxocarbonate and calcium trioxocarbonate. However, when it react with calcium sulphate, calcium carbonate and sodium tetraoxosulphate is formed
Source: Myschool Past Questions Archive (Record #47675)
Chemistry
UTME / JAMB 2018
Nature of Matter & Separation Techniques
Solution
Which of the following separation techniques can be employed in obtaining solvent from its solution?
A
Evaporation
B
Distillation
C
Filtration
D
Precipitation
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Distillation is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation.
Source: Myschool Past Questions Archive (Record #47676)
Chemistry
UTME / JAMB 2018
Air & Environmental Chemistry
Solution
In the upper atmosphere, the ultra-violet light breaks off a free chlorine atom from chlorofluorocarbon molecule. The effect of this is that the free chlorine atom will
A
be very reactive and will attack ozone
B
be non-reactive and will not attack ozone
C
not change the level of ozone in the atmosphere
D
increase the level of ozone in the atmosphere
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
CFCs (Chlorofluorocarbons) have a lifetime in the atmosphere of about 20 to 100 years, and consequently one free chlorine atom from a CFC molecule can do a lot of damage, destroying ozone molecules for a long time
Source: Myschool Past Questions Archive (Record #47677)
Chemistry
WAEC / WASSCE 2018
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
Which of the following raw materials is used in the plastic industry?
A
Ethene
B
Methane
C
Sulphur
D
Hydrogen
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Ethene is the most important organic chemical, by weight, that is manufactured. It is an important raw material for the production of plastics and antifreeze solutions as well as solvents.
Source: Myschool Past Questions Archive (Record #48956)
Chemistry
WAEC / WASSCE 2018
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
Which of the following organic compounds can undergo both addition and substitution reactions?
A
Pentane
B
Benzene
C
Propane
D
Hexane
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
An example of benzene addition reaction is the formation of cyclohexane by a mix of benzene vapour and hydrogen passed over nickel catalyst; while chlorobenzene is formed by substitution reaction.
Source: Myschool Past Questions Archive (Record #48957)
Chemistry
WAEC / WASSCE 2018
Chemical Bonding & Intermolecular Forces
Solution
In which of the following compounds does hydrogen form ionic compounds?
A
C\(H_4\)
B
HCl
C
N\(H_3\)
D
NaH
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The bonding between a non-metal and a metal is an ionic bonding. In metal hydrides, Hydrogen takes on the ionic charge of -1, hence forming an ionic bond with the metals.
Source: Myschool Past Questions Archive (Record #48969)
Chemistry
WAEC / WASSCE 2018
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
An organic compound has the empirical formula \(CH_{2}\). If its molar mass is 42\(gmol^{-1}\), what is its molecular formula? (C = 12.0, H = 1.0)
A
\(C_{2}H_{4}\)
B
\(C_{3}H_{4}\)
C
\(C_{3}H_{6}\)
D
\(C_{4}H_{8}\)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Given the molecular formula, \(CH_{2}\).
The empirical formula will be \((CH_{2})n\)= 42
\((12+(2\times1))n =42\)
⇒ \(14n =42\)
n = 3, hence the empirical formula is \(C_{3}H_{6}\)
Source: Myschool Past Questions Archive (Record #48970)
Chemistry
WAEC / WASSCE 2018
Oxidation, Reduction & Redox Reactions
Consider the following reaction equation: \(Br_{2} + 2KI \to 2KBr + I_{2}\). Bromine is acting as
A
an oxidizing agent
B
a reducing agent
C
an acid
D
a base
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #48973)
Chemistry
WAEC / WASSCE 2018
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
Ethene is produced from ethanol by
A
decomposition
B
hydrolysis
C
ozonolysis
D
dehydration
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Ethene can be gotten from the dehydration of ethanol in the presence of excess \(H_{2}SO_{4}\) or \(H_{3}PO_{4}\).
Source: Myschool Past Questions Archive (Record #48986)
Chemistry
WAEC / WASSCE 2018
Reaction Rates & Chemical Equilibrium
Solution
Consider the following equilibrium reaction: \(2AB_{{2}{(g)}} + B_{{2}{(g)}} \to 2AB_{{3}{(g)}}\). \(\Delta H= -X kJmol^{-1}\). The backward reaction will be favored by
A
a decrease in pressure
B
an increase in pressure
C
a decrease in temperature
D
an introduction of a positive catalyst
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
The equilibrium position is shifted to the left with a decrease in pressure in this system because the number of gaseous molecules on the right is less. (Le-Chatelier's principle).
Source: Myschool Past Questions Archive (Record #49003)
Chemistry
WAEC / WASSCE 2018
Electrolysis & Electrochemical Cells
Solution
The preferential discharge of ions during electrolysis is influenced by the
A
mechanism of electrolysis
B
electrolytic reactions
C
nature of the electrode
D
type of electrolytic cell
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The preferential discharge of ions is influenced by:
- The position of the ions in the electrochemical series
- The concentration of the ions in the electrolyte
- The nature of the electrode
Source: Myschool Past Questions Archive (Record #49048)