MCQ 31
What does a balanced chemical equation represent?
A) The energy changes during a reaction
B) The physical states of reactants and products
C) The conservation of mass
D) The rates of reaction
Answer: C) The conservation of mass.
Explanation: A balanced equation indicates that the number of atoms of each element is conserved, reflecting the Law of Conservation of Mass.
MCQ 32
In the chemical formula C₆H₁₂O₆, what does the “6” before carbon signify?
A) The number of carbon atoms
B) The mass of carbon
C) The number of oxygen atoms
D) The total number of atoms
Answer: A) The number of carbon atoms.
Explanation: The “6” indicates that there are six carbon atoms in the glucose molecule.
MCQ 33
Which of the following statements about the Law of Conservation of Mass is true?
A) It applies only to physical changes.
B) It was first formulated by Albert Einstein.
C) It states that mass can be converted into energy.
D) It applies to all chemical reactions.
Answer: D) It applies to all chemical reactions.
Explanation: The Law of Conservation of Mass is applicable to all chemical reactions, emphasizing that mass remains constant.
MCQ 34
Which of the following describes a fixed ratio in the context of chemical compounds?
A) H₂ and O₂ combine in a variable ratio.
B) NaCl always contains 1:1 ratio of sodium to chlorine.
C) All molecules have different ratios of atoms.
D) Elements can combine in any ratio.
Answer: B) NaCl always contains 1:1 ratio of sodium to chlorine.
Explanation: The composition of NaCl is fixed, always comprising one sodium atom for each chlorine atom.
MCQ 35
What is the outcome when nitrogen and hydrogen react to form ammonia?
A) Fixed mass is lost.
B) New elements are formed.
C) Mass is conserved.
D) Energy is destroyed.
Answer: C) Mass is conserved.
Explanation: In the reaction between nitrogen and hydrogen to form ammonia, the total mass of the reactants equals the total mass of ammonia produced.
MCQ 36
What does the Law of Multiple Proportions apply to?
A) Mixtures of elements
B) Different compounds formed from the same elements
C) Physical changes only
D) The states of matter
Answer: B) Different compounds formed from the same elements.
Explanation: This law pertains to how two elements can combine in different ratios to form various compounds.
MCQ 37
When sodium reacts with chlorine, what is the resulting compound?
A) NaCl
B) NaCl₂
C) Na₂Cl
D) Na₂Cl₂
Answer: A) NaCl.
Explanation: Sodium and chlorine react in a 1:1 ratio to form sodium chloride (NaCl).
MCQ 38
Which of the following is an implication of Dalton’s Atomic Theory?
A) All substances are made of molecules.
B) Atoms can be split into smaller parts.
C) Chemical reactions involve the rearrangement of atoms.
D) Elements can vary in their atomic weights.
Answer: C) Chemical reactions involve the rearrangement of atoms.
Explanation: Dalton’s theory states that atoms are rearranged during chemical reactions, which supports the idea of conservation of mass.
MCQ 39
What principle underlies stoichiometry in chemical reactions?
A) Law of Conservation of Energy
B) Law of Definite Proportions
C) Law of Multiple Proportions
D) Law of Conservation of Mass
Answer: D) Law of Conservation of Mass.
Explanation: Stoichiometry is based on the principle that mass is conserved in chemical reactions, allowing the calculation of reactants and products.
MCQ 40
What does the term “stoichiometry” refer to?
A) The study of the properties of gases
B) The calculation of reactants and products in chemical reactions
C) The relationship between temperature and pressure
D) The measurement of physical changes
Answer: B) The calculation of reactants and products in chemical reactions.
Explanation: Stoichiometry involves the quantitative relationships between the substances involved in a chemical reaction.
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