MCQ 81
Which of the following is an example of a chemical change?
A) Ice melting
B) Dissolving salt in water
C) Burning wood
D) Boiling water
Answer: C) Burning wood.
Explanation: Burning wood is a chemical change as it produces new substances (ash, smoke) and involves a chemical reaction with oxygen.
MCQ 82
Which type of radiation has the highest penetrating power?
A) Alpha particles
B) Beta particles
C) Gamma rays
D) Ultraviolet rays
Answer: C) Gamma rays.
Explanation: Gamma rays have the highest penetrating power and can pass through most materials, requiring dense substances like lead for shielding.
MCQ 83
What is the main feature of a base?
A) Produces hydrogen ions in solution
B) Produces hydroxide ions in solution
C) Tastes sour
D) Turns blue litmus paper red
Answer: B) Produces hydroxide ions in solution.
Explanation: Bases produce hydroxide ions (OH⁻) in solution, which is a key characteristic of basic substances.
MCQ 84
What happens to the volume of a gas when its temperature increases at constant pressure?
A) Volume decreases.
B) Volume remains the same.
C) Volume increases.
D) Volume fluctuates.
Answer: C) Volume increases.
Explanation: According to Charles’s Law, at constant pressure, the volume of a gas increases as the temperature increases.
MCQ 85
Which of the following best defines a mole?
A) A measure of mass.
B) A measure of volume.
C) A unit of quantity representing 6.022 × 10²³ particles.
D) A measure of energy.
Answer: C) A unit of quantity representing 6.022 × 10²³ particles.
Explanation: A mole is defined as the amount of substance that contains the same number of entities (atoms, molecules, etc.) as there are in 12 grams of carbon-12.
MCQ 86
Which of the following is true about a chemical equilibrium?
A) The concentrations of reactants and products remain constant.
B) The reaction has stopped completely.
C) The forward reaction occurs faster than the reverse reaction.
D) There is no energy exchange.
Answer: A) The concentrations of reactants and products remain constant.
Explanation: In chemical equilibrium, the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products.
MCQ 87
What does the term “solubility” refer to?
A) The amount of solute that can be dissolved in a given amount of solvent at a specific temperature.
B) The ability of a solute to conduct electricity.
C) The measure of pH in a solution.
D) The speed of dissolution.
Answer: A) The amount of solute that can be dissolved in a given amount of solvent at a specific temperature.
Explanation: Solubility is a quantitative measure of how much solute can dissolve in a specific quantity of solvent at a given temperature.
MCQ 88
What is the primary product of the electrolysis of water?
A) Oxygen gas
B) Hydrogen gas
C) Ozone
D) Hydrogen peroxide
Answer: B) Hydrogen gas.
Explanation: The electrolysis of water primarily produces hydrogen gas at the cathode and oxygen gas at the anode.
MCQ 89
Which of the following processes increases the concentration of a solution?
A) Dilution
B) Evaporation
C) Filtration
D) Distillation
Answer: B) Evaporation.
Explanation: Evaporation removes solvent from a solution, thereby increasing the concentration of solute remaining.
MCQ 90
What is the effect of increasing the concentration of reactants on the rate of a chemical reaction?
A) Rate decreases.
B) Rate increases.
C) No effect.
D) Rate becomes constant.
Answer: B) Rate increases.
Explanation: Increasing the concentration of reactants generally increases the rate of reaction due to a higher probability of collisions between reactant molecules.
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