MCQ 71
Which chemical equation is balanced?
A) H₂ + O₂ → H₂O
B) 2H₂ + O₂ → 2H₂O
C) C + O₂ → CO
D) 2C + O₂ → 2CO
Answer: B) 2H₂ + O₂ → 2H₂O.
Explanation: This equation has equal numbers of each type of atom on both sides, making it balanced.
MCQ 72
What is the primary factor that determines the coefficients in a balanced equation?
A) Temperature
B) Pressure
C) Conservation of mass
D) Reactant concentration
Answer: C) Conservation of mass.
Explanation: Coefficients are determined to ensure that the total mass of reactants equals the total mass of products.
MCQ 73
Which of the following indicates a physical change?
A) Rusting of iron
B) Burning of wood
C) Dissolving salt in water
D) Baking a cake
Answer: C) Dissolving salt in water.
Explanation: Dissolving is a physical change; the salt can be recovered by evaporating the water.
MCQ 74
What does Avogadro’s Law state about equal volumes of gases?
A) They have the same mass.
B) They contain the same number of moles.
C) They have different molecular weights.
D) They are in different states of matter.
Answer: B) They contain the same number of moles.
Explanation: Avogadro’s Law states that equal volumes of gases at the same temperature and pressure contain an equal number of moles.
MCQ 75
When zinc reacts with hydrochloric acid, what is produced?
A) Zinc chloride and hydrogen gas
B) Zinc oxide and water
C) Zinc sulfate and oxygen
D) Zinc hydroxide and chlorine gas
Answer: A) Zinc chloride and hydrogen gas.
Explanation: The reaction of zinc with hydrochloric acid produces zinc chloride (ZnCl₂) and hydrogen gas (H₂).
MCQ 76
In a chemical reaction, what does it mean if a substance is oxidized?
A) It gains electrons.
B) It loses electrons.
C) It gains protons.
D) It loses neutrons.
Answer: B) It loses electrons.
Explanation: Oxidation refers to the loss of electrons during a chemical reaction.
MCQ 77
Which element typically undergoes reduction in a redox reaction?
A) The oxidizing agent
B) The reducing agent
C) The solvent
D) The catalyst
Answer: A) The oxidizing agent.
Explanation: The oxidizing agent gains electrons and is reduced during a redox reaction.
MCQ 78
Which of the following represents a heterogeneous mixture?
A) Saltwater
B) Air
C) Salad
D) Sugar solution
Answer: C) Salad.
Explanation: A salad contains visibly different components, making it a heterogeneous mixture.
MCQ 79
What type of reaction is represented by the equation: 2Na + Cl₂ → 2NaCl?
A) Decomposition
B) Synthesis
C) Combustion
D) Double replacement
Answer: B) Synthesis.
Explanation: This reaction shows two reactants combining to form a single product, NaCl.
MCQ 80
What is the outcome of a double replacement reaction?
A) Reactants form a single product.
B) Atoms are rearranged to form new substances.
C) One element replaces another in a compound.
D) Two compounds exchange ions to form new compounds.
Answer: D) Two compounds exchange ions to form new compounds.
Explanation: In a double replacement reaction, two compounds react and exchange their ions.
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