MCQ 91
Which law states that all gases at the same temperature and pressure occupy the same volume?
A) Boyle’s Law
B) Charles’s Law
C) Avogadro’s Law
D) Dalton’s Law
Answer: C) Avogadro’s Law.
Explanation: Avogadro’s Law states that equal volumes of gases contain an equal number of molecules at the same temperature and pressure.
MCQ 92
What is produced when an acid reacts with a metal carbonate?
A) Salt and water
B) Salt and hydrogen gas
C) Salt, water, and carbon dioxide
D) Only salt
Answer: C) Salt, water, and carbon dioxide.
Explanation: The reaction produces salt, water, and carbon dioxide gas.
MCQ 93
Which of the following is a characteristic of ionic compounds?
A) They are poor conductors of electricity.
B) They have low melting points.
C) They are soluble in water.
D) They are gaseous at room temperature.
Answer: C) They are soluble in water.
Explanation: Ionic compounds generally dissolve in water and conduct electricity when dissolved.
MCQ 94
What does the term “stoichiometric coefficients” refer to in a balanced equation?
A) The ratios of heat produced
B) The number of moles of each substance
C) The weight of reactants
D) The types of bonds formed
Answer: B) The number of moles of each substance.
Explanation: Stoichiometric coefficients indicate the number of moles of each reactant and product in a balanced equation.
MCQ 95
Which of the following reactions is an example of a single replacement reaction?
A) 2H₂ + O₂ → 2H₂O
B) Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag
C) CaCO₃ → CaO + CO₂
D) NaCl + KBr → NaBr + KCl
Answer: B) Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag.
Explanation: In a single replacement reaction, one element replaces another in a compound.
MCQ 96
In the context of chemical reactions, what does the term “yield” refer to?
A) The temperature at which a reaction occurs
B) The amount of product formed
C) The time taken for a reaction
D) The energy released
Answer: B) The amount of product formed.
Explanation: Yield refers to the quantity of product obtained from a chemical reaction.
MCQ 97
Which of the following is a sign of a chemical change?
A) Change in size
B) Change in shape
C) Change in color
D) Change in state
Answer: C) Change in color.
Explanation: A change in color often indicates a chemical change, whereas size or shape may indicate a physical change.
MCQ 98
What does a catalyst do in a chemical reaction?
A) Increases the mass of reactants
B) Decreases the reaction rate
C) Lowers the activation energy
D) Changes the products formed
Answer: C) Lowers the activation energy.
Explanation: A catalyst speeds up a reaction by lowering the activation energy required for the reaction to proceed.
MCQ 99
In a chemical reaction, if 10 g of reactants produce 8 g of products, what can be inferred?
A) Mass was lost.
B) There was an error in measurement.
C) The reaction was incomplete.
D) Mass is conserved.
Answer: D) Mass is conserved.
Explanation: The law of conservation of mass states that mass cannot be lost in a reaction; the discrepancy might be due to measurement error or gas release.
MCQ 100
What is the molar volume of an ideal gas at standard temperature and pressure (STP)?
A) 22.4 L
B) 24.0 L
C) 18.0 L
D) 30.0 L
Answer: A) 22.4 L.
Explanation: At STP, one mole of an ideal gas occupies 22.4 liters.
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