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Chemistry
WAEC / WASSCE 2019
Acids, Bases, and Salts
Solution
If 6.5g of magnesium ribbon reacts completely with Hydrochloric acid, how many grams of hydrogen gas would be liberated?
Mg(s) + 2 HCl(aq) --> MgCl 2(aq) + H 2(g)
[ H = 1.0, Mg = 24.0 ]
A
0.54g
B
0.70g
C
1.08g
D
1.40g
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
24g of Mg will liberate 2g of H
: 6.5g of Mg will liberate Xg of H
= ( 6.5 X 2 ) / 24
= 0.5416g of Hygrogen ( H )
Source: Myschool Past Questions Archive (Record #57983)
Chemistry
WAEC / WASSCE 2019
Atomic Structure and Periodic Table
Calcium and magnesium belong to the group of the periodic table because both?
A
are metals
B
form cations
C
form colourless salts
D
have same number of valence electrons
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #57984)
Chemistry
WAEC / WASSCE 2019
Atomic Structure and Periodic Table
Solution
The periodic table is an arrangement of elements according to their?
A
Oxidation number
B
Atomic number
C
Mass number
D
Number of neutrons
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Elements are arranged in order of increasing atomic number
Source: Myschool Past Questions Archive (Record #57835)
Chemistry
WAEC / WASSCE 2019
Atomic Structure and Periodic Table
Solution
A solid with higher melting and boiling points is likely to be?
A
Covalent compound
B
A Dative compound
C
An Electrovalent compound
D
A Non-metal
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Ionic Compounds / Electrovalent compounds Have A High Melting Point and High Boiling Point.
Source: Myschool Past Questions Archive (Record #57872)
Chemistry
WAEC / WASSCE 2019
Atomic Structure and Periodic Table
Solution
Which of the substances is non-polar?
A
Bromine
B
Ammonia
C
Water
D
Hydrogen Bromide
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Br2 (Bromine) is nonpolar because, in this molecule, both bromine atoms have the same electronegativity due to which both atoms have equal charge distribution and results in a net-zero dipole moment.
Source: Myschool Past Questions Archive (Record #57990)
Chemistry
WAEC / WASSCE 2019
Stoichiometry & Mole Concept
Solution
Which of the following pairs of components have the same molecular mass?
[ H = 1.0, C = 12.0, O = 16.0 ]
A
Ethene and Ethyne
B
Ethane and Ethene
C
Carbon (ii) Oxide and Ethene
D
Carbon (iv) Oxide and Ethyne
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Ethene = 28
Ethyne = 26
Carbon(ii)Oxide = 28
Carbon(iv)Oxide = 44
Source: Myschool Past Questions Archive (Record #58022)
Chemistry
WAEC / WASSCE 2019
Kinetics, Energetics and Equilibrium
Solution
When an equilibrium is established between dissolved and undissolved solutes, the solution is said to be?
A
Saturated
B
Unsaturated
C
Concentrated
D
Diluted
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
The term saturated solution is defined in chemistry as a solution in which no more solute can be dissolved in the solvent.
Source: Myschool Past Questions Archive (Record #58024)
Chemistry
WAEC / WASSCE 2019
Stoichiometry & Mole Concept
Solution
How many moles of carbon(iv)oxide contains 16.0g of oxygen?
[ C = 12.0, O = 16.0 ]
A
0.20 mol
B
0.25 mol
C
0.40 mol
D
0.50 mol
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
1 Mole of carbon(iv)oxide contains 32g of Oxygen
: 0.5 Mole of carbon(iv)oxide contains 16g of Oxygen
Source: Myschool Past Questions Archive (Record #58026)
Chemistry
WAEC / WASSCE 2019
Stoichiometry & Mole Concept
Solution
Stoichiometry is based on the law?
A
multiple proportion
B
constant composition
C
conservation of energy
D
conservation of mass
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The principles of stoichiometry are based upon the law of conservation of mass. Matter can neither be created nor destroyed, so the mass of every element present in the product(s) of a chemical reaction must be equal to the mass of each and every element present in the reactant(s).
Source: Myschool Past Questions Archive (Record #58028)
Chemistry
WAEC / WASSCE 2019
Stoichiometry & Mole Concept
Solution
What is the percentage by mass of H in CH\(_3\)COOH ?
A
1.7%
B
5.0%
C
6.7%
D
7.1%
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
- molecular mass (or molar mass) is 60.05 g/mol
- with 4 atoms of hydrogen present
( 4 / 60 ) X 100
≈6.7%
Source: Myschool Past Questions Archive (Record #58030)
Chemistry
WAEC / WASSCE 2019
Atomic Structure and Periodic Table
Solution
Which of the following compounds has coordinate bonds in its structure?
A
Al\(_2\)Cl\(_6\)
B
MgCl\(_2\)
C
AgCl
D
NaCl
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Aluminum chloride (Al2Cl6) has coordinate dative bonding
In the solid state, aluminum chloride forms a dimer (Al₂Cl₆) where two aluminum atoms are connected by coordinate covalent bonds with chlorine atoms, stabilizing the structure.
Source: Myschool Past Questions Archive (Record #58033)
Chemistry
WAEC / WASSCE 2019
Matter & Separation Techniques
Solution
The name of the compound CH\(_3\)C(CH\(_3\))\(_2\)CH\(_2\)CH\(_2\)CH\(_3\)
A
2 - methyl butane
B
2,2 - dimethyl butane
C
2 - methyl pentane
D
2,2 - dimethyl pentane
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
- The longest chain has five carbon atoms i.e PENT
- with two methyl attached to the second carbon atom
Source: Myschool Past Questions Archive (Record #58035)
Chemistry
WAEC / WASSCE 2019
Stoichiometry & Mole Concept
Solution
What is the solubility of a salt X at 25ºC if the saturated solution of the salt contains 0.28g in 100cm\(^3\) of the solution in mol\dm\(^3\)?
[ X = 56.0g ]
A
0.05
B
0.10
C
2.60
D
2.80
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
(mass / molar mass) X (1000 / vol )
(0.28 / 56.0) X (1000 / 100 )
= 2.8 / 56
= 0.05 mol\dm\(^3\)
Source: Myschool Past Questions Archive (Record #58047)
Chemistry
WAEC / WASSCE 2019
Acids, Bases, and Salts
Solution
Vinegar is an aqueous solution of?
A
Hydrochloric acid
B
ethanedioc acid
C
ethanoic acid
D
hydrofluoric acid
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings.
Source: Myschool Past Questions Archive (Record #58050)
Chemistry
WAEC / WASSCE 2019
Stoichiometry & Mole Concept
Solution
which of the following solutions containing one mole per dm\(^3\) of the compound would have the lowest PH?
A
ethanoic acid
B
hydrochloric acid
C
sodium chloride
D
sodium hydrogentrioxocarbonate(iv)
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Low PH means strongly acidic cause acidity increases with decreasing PH values.
Example is Hydrochloric Acid
Source: Myschool Past Questions Archive (Record #58093)