Chemical Formulae and Equations Practice Questions
SPM (Malaysia) · SPM Chemistry · 138 free MCQs with instant results and detailed explanations.
138
Total
40
Easy
71
Medium
27
Hard
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Sample Questions from Chemical Formulae and Equations
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Q1
Easy
What is the chemical formula for water?
A.
H2O
B.
CO2
C.
O2
D.
H2O2
Show Answer & Explanation
Correct Answer: A
Water is composed of two hydrogen atoms and one oxygen atom, represented by the formula H2O.
Q2
Easy
What is the balanced equation for the combustion of propane (C3H8)?
A.
C3H8 + 5O2 → 3CO2 + 4H2O
B.
C3H8 + 4O2 → 3CO2 + 6H2O
C.
C3H8 + 3O2 → 3CO2 + 2H2O
D.
C3H8 + 2O2 → 3CO2 + H2O
Show Answer & Explanation
Correct Answer: A
The correct balanced equation shows that one molecule of propane reacts with five molecules of oxygen to produce three molecules of carbon dioxide and four molecules of water.
Q3
Easy
Which of the following represents the correct empirical formula for glucose (C6H12O6)?
A.
CH2O
B.
C2H4O2
C.
C6H12O6
D.
C3H6O3
Show Answer & Explanation
Correct Answer: A
The empirical formula shows the simplest whole number ratio of the elements in glucose, which is 1:2:1 for carbon, hydrogen, and oxygen respectively, written as CH2O.
Q4
Medium
What is the empirical formula of glucose (C6H12O6)?
A.
C2H4O2
B.
CHO
C.
C6H12O6
D.
C3H6O3
Show Answer & Explanation
Correct Answer: B
The empirical formula is the simplest ratio of the elements in a compound. For glucose, its molecular formula is C6H12O6, which simplifies to CHO.
Q5
Medium
When balancing the equation: _H2 + _O2 -> _H2O, what is the coefficient of O2?
A.
1
B.
2
C.
3
D.
4
Show Answer & Explanation
Correct Answer: A
To balance the equation, we find that two hydrogen molecules react with one oxygen molecule to produce two water molecules, making the coefficient of O2 equal to 1.
Q6
Medium
Which of the following compounds has a molecular formula of C4H10?
A.
Butane
B.
Propane
C.
Ethane
D.
Pentane
Show Answer & Explanation
Correct Answer: A
Butane has the molecular formula C4H10, while propane (C3H8), ethane (C2H6), and pentane (C5H12) have different molecular formulas.
Q7
Medium
What is the total number of atoms in one molecule of calcium carbonate (CaCO3)?
A.
3
B.
5
C.
4
D.
6
Show Answer & Explanation
Correct Answer: B
Calcium carbonate consists of one calcium atom, one carbon atom, and three oxygen atoms. Therefore, the total number of atoms is 1 + 1 + 3 = 5.
Q8
Hard
What is the empirical formula of a compound containing 40% Carbon, 6.7% Hydrogen, and 53.3% Oxygen by mass?
A.
C2H4O3
B.
C3H6O4
C.
CH2O
D.
C1H2O1
Show Answer & Explanation
Correct Answer: C
To find the empirical formula, we convert mass percentages to moles. The molar mass of C, H, and O is approximately 12, 1, and 16 g/mol respectively. Calculating moles: C = 40g/12g/mol = 3.33, H = 6.7g/1g/mol = 6.7, O = 53.3g/16g/mol = 3.33. The ratio of moles is approximately 1:2:1, giving the empirical formula CH2O.
Q9
Hard
A reaction produces 4.5 grams of water from 2 grams of hydrogen gas and 16 grams of oxygen gas. Which of the following statements is correct regarding the reaction?
A.
The reaction violates the law of conservation of mass.
B.
The reaction shows a 100% yield.
C.
Hydrogen is the limiting reagent.
D.
Oxygen is in excess in the reaction.
Show Answer & Explanation
Correct Answer: C
To determine the limiting reagent, we need to check how much water can be produced by each reactant. The balanced equation for the formation of water is 2H2 + O2 → 2H2O. From 2g of H2 (approximately 1 mole), we can produce 18g of water, which is more than 4.5g, indicating that H2 is limiting since O2 (16g) can produce more than 4.5g of water.
Q10
Hard
In a chemical reaction, 4 moles of ammonium sulfate reacts with excess sodium hydroxide to produce ammonia gas and water. What is the balanced chemical equation for this reaction?
A.
4 NH4SO4 + 4 NaOH → 4 NH3 + 4 H2O + 4 Na2SO4
B.
4 NH4SO4 + 4 NaOH → 4 NH3 + 4 H2O + 2 Na2SO4
C.
4 NH4SO4 + 4 NaOH → 4 NH3 + 2 H2O + 4 Na2SO4
D.
2 NH4SO4 + 2 NaOH → 2 NH3 + 2 H2O + 2 Na2SO4
Show Answer & Explanation
Correct Answer: B
The balanced equation shows that 4 moles of ammonium sulfate react with 4 moles of sodium hydroxide to produce 4 moles of ammonia and 4 moles of water along with 2 moles of sodium sulfate, ensuring mass conservation.
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Chemical Formulae and Equations — SPM (Malaysia) SPM Chemistry Practice Questions Online
This page contains 138 practice MCQs for the chapter Chemical Formulae and Equations in SPM (Malaysia) SPM Chemistry. The questions are organized by difficulty — 40 easy, 71 medium, 27 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.