Chemical Combination Practice Questions
WAEC (West Africa) · WAEC Chemistry · 146 free MCQs with instant results and detailed explanations.
146
Total
49
Easy
72
Medium
25
Hard
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Sample Questions from Chemical Combination
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Q1
Easy
What is the product of the reaction between magnesium and oxygen?
A.
Magnesium oxide
B.
Magnesium peroxide
C.
Magnesium hydroxide
D.
Magnesium nitride
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Correct Answer: A
When magnesium reacts with oxygen, it forms magnesium oxide (MgO), a basic oxide, through a combustion reaction.
Q2
Easy
Which of the following is an example of a synthesis reaction?
A.
A + B → AB
B.
AB → A + B
C.
A + BC → AC + B
D.
AB + CD → AC + BD
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Correct Answer: A
A synthesis reaction occurs when two or more reactants combine to form a single product, as shown in A + B → AB.
Q3
Easy
If 2 moles of hydrogen gas combine with 1 mole of oxygen gas, what is the maximum amount of water produced?
A.
1 mole
B.
2 moles
C.
3 moles
D.
4 moles
Show Answer & Explanation
Correct Answer: B
The balanced equation 2H2 + O2 → 2H2O indicates that 2 moles of hydrogen gas produce 2 moles of water.
Q4
Medium
What is the result of combining one mole of hydrogen gas with half a mole of oxygen gas under ideal conditions?
A.
Water
B.
Hydrogen peroxide
C.
Ozone
D.
Hydrogen oxide
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Correct Answer: A
The reaction between hydrogen and oxygen gas produces water (H2O). One mole of hydrogen combines with half a mole of oxygen to yield one mole of water.
Q5
Medium
In the reaction between sodium and chlorine, what is the type of chemical combination taking place?
A.
Synthesis reaction
B.
Decomposition reaction
C.
Single displacement reaction
D.
Double displacement reaction
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Correct Answer: A
The reaction between sodium and chlorine produces sodium chloride (NaCl) through a synthesis process where two reactants form a single product.
Q6
Medium
Which of the following represents a balanced chemical equation for the combination of magnesium and oxygen?
A.
2Mg + O2 → 2MgO
B.
Mg + O2 → MgO
C.
Mg + 2O2 → MgO2
D.
2Mg + 2O2 → 2MgO2
Show Answer & Explanation
Correct Answer: A
The correct balanced equation is 2Mg + O2 → 2MgO, which shows that two moles of magnesium react with one mole of oxygen to form two moles of magnesium oxide.
Q7
Medium
When sulfur burns in oxygen, what compound is primarily formed?
A.
Sulfur dioxide
B.
Sulfur trioxide
C.
Sulfuric acid
D.
Thiosulfuric acid
Show Answer & Explanation
Correct Answer: A
The primary product formed when sulfur combusts in oxygen is sulfur dioxide (SO2), as it reacts to produce this compound under normal combustion conditions.
Q8
Hard
A compound is formed when nitrogen reacts with hydrogen. What is the balanced equation for the formation of ammonia (NH3) from its elements?
A.
N2 + 3H2 → 2NH3
B.
N2 + H2 → NH3
C.
2N2 + 3H2 → 2NH3
D.
N2 + 2H2 → NH3
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Correct Answer: A
The balanced equation N2 + 3H2 → 2NH3 correctly reflects the conservation of mass with 2 nitrogen and 6 hydrogen atoms on both sides, complying with stoichiometric principles.
Q9
Hard
Which of the following statements about chemical bonds in a molecule of water (H2O) is correct?
A.
Water has polar covalent bonds due to the difference in electronegativity between hydrogen and oxygen.
B.
Water has non-polar covalent bonds because the electronegativity of hydrogen and oxygen is identical.
C.
Water molecules are held together by ionic bonds.
D.
Water has covalent bonds with equal sharing of electrons between hydrogen and oxygen.
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Correct Answer: A
Water has polar covalent bonds because oxygen is more electronegative than hydrogen, resulting in an unequal sharing of electrons and creating a dipole.
Q10
Hard
Which of the following represents the correct stoichiometric coefficients for the balanced chemical equation of the reaction between nitrogen and hydrogen to form ammonia?
A.
1 N2 + 3 H2 → 2 NH3
B.
1 N2 + 2 H2 → 2 NH3
C.
2 N2 + 3 H2 → 6 NH3
D.
1 N2 + 1 H2 → 1 NH3
Show Answer & Explanation
Correct Answer: A
The reaction between nitrogen and hydrogen to form ammonia is represented by the equation 1 N2 + 3 H2 → 2 NH3. This shows that one mole of nitrogen reacts with three moles of hydrogen to produce two moles of ammonia, which is the correct stoichiometric representation.
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Chemical Combination — WAEC (West Africa) WAEC Chemistry Practice Questions Online
This page contains 146 practice MCQs for the chapter Chemical Combination in WAEC (West Africa) WAEC Chemistry. The questions are organized by difficulty — 49 easy, 72 medium, 25 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.