MCQ 81
What is the empirical formula for C₃H₆?
A) C₃H₆
B) C₁H₂
C) C₂H₄
D) C₃H₆O
Answer: B) C₁H₂.
Explanation: The empirical formula represents the simplest whole number ratio of atoms, which is C₁H₂ for C₃H₆.
MCQ 82
Which of the following is a product of the combustion of hydrocarbons?
A) Water
B) Carbon dioxide
C) Energy
D) All of the above
Answer: D) All of the above.
Explanation: Combustion of hydrocarbons produces water, carbon dioxide, and releases energy.
MCQ 83
According to the Law of Conservation of Mass, what happens to the mass during a reaction?
A) It is created.
B) It is destroyed.
C) It remains constant.
D) It changes form.
Answer: C) It remains constant.
Explanation: The total mass of reactants equals the total mass of products, thus remaining constant.
MCQ 84
What type of reaction is represented by the equation: 2H₂ + O₂ → 2H₂O?
A) Synthesis
B) Decomposition
C) Combustion
D) Single replacement
Answer: A) Synthesis.
Explanation: This equation shows two reactants combining to form a single product, water.
MCQ 85
What is the mass of 1 mole of any element equal to?
A) The number of protons
B) The atomic weight in grams
C) The density of the element
D) The volume at STP
Answer: B) The atomic weight in grams.
Explanation: The molar mass of an element is numerically equal to its atomic weight expressed in grams.
MCQ 86
Which gas is commonly produced in acid-base reactions?
A) Oxygen
B) Hydrogen
C) Nitrogen
D) Carbon dioxide
Answer: B) Hydrogen.
Explanation: Many acid-base reactions, particularly with metals, produce hydrogen gas as a byproduct.
MCQ 87
Which of the following laws applies to reactions involving mixtures?
A) Law of Definite Proportions
B) Law of Multiple Proportions
C) Law of Conservation of Mass
D) Dalton’s Law
Answer: C) Law of Conservation of Mass.
Explanation: This law applies to mixtures and reactions, stating that mass is conserved in all reactions.
MCQ 88
What is the significance of a balanced equation?
A) It shows energy changes.
B) It represents the types of bonds.
C) It indicates the physical states of reactants.
D) It reflects the conservation of mass.
Answer: D) It reflects the conservation of mass.
Explanation: A balanced equation ensures that the number of atoms for each element is the same on both sides, reflecting mass conservation.
MCQ 89
Which of the following processes is a physical change?
A) Burning wood
B) Dissolving sugar in water
C) Rusting iron
D) Cooking an egg
Answer: B) Dissolving sugar in water.
Explanation: Dissolving sugar in water is a physical change since it can be reversed by evaporation.
MCQ 90
In a redox reaction, what does the reducing agent do?
A) Gains electrons
B) Loses electrons
C) Increases energy
D) Decreases mass
Answer: B) Loses electrons.
Explanation: The reducing agent donates electrons and is oxidized in the process.
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