MCQs — Energetics

Practice questions for Chemistry.

Question 81

A substance that accelerates a chemical reaction but remains chemically unchanged at the end of the reaction is called a:

A. Reactant

B. Catalyst

C. Product

D. Spectator ion

Question 82

The phenomenon in which a catalyst accelerates a chemical reaction is called:

A. Catalysis

B. Oxidation

C. Neutralization

D. Sublimation

Question 83

A catalyst increases the rate of a reaction mainly by:

A. Increasing the overall enthalpy of the reaction

B. Providing a new reaction mechanism with a lower activation energy

C. Increasing the mass of the reactants

D. Removing the need for any reactants at all

Question 84

In the bodies of living organisms, which biological catalysts are responsible for catalyzing chemical reactions?

A. Hormones

B. Enzymes

C. Vitamins only

D. Antibodies

Question 85

Why might many industrial reactions rely on adding a catalyst rather than simply increasing the temperature to speed up the reaction?

A. Because high-temperature reactions can cause safety problems, and many chemicals are not stable at high temperatures, so a catalyst offers a safer alternative

B. Because catalysts always work faster than heating, with no other benefit

C. Because increasing temperature is illegal in industrial settings

D. Because catalysts are always cheaper than heating equipment

Question 86

Does a catalyst change the overall enthalpy (thermodynamics) of a reaction?

A. Yes, a catalyst always increases the overall enthalpy change

B. No, a catalyst does not affect the overall enthalpy or thermodynamics of the reaction; it only affects the rate

C. Yes, a catalyst always decreases the overall enthalpy change

D. A catalyst has no effect on a reaction whatsoever

Question 87

On a reaction-progress energy diagram comparing catalyzed and uncatalyzed pathways, how would the catalyzed pathway's activation energy compare to the uncatalyzed pathway's?

A. The catalyzed pathway would show a higher activation energy peak

B. The catalyzed pathway would show a lower activation energy peak than the uncatalyzed pathway

C. Both pathways would show identical activation energy peaks

D. Activation energy is not shown on such diagrams

Question 88

Since a catalyst remains chemically unchanged at the end of a reaction, what does this imply about the amount of catalyst needed?

A. A very large excess of catalyst is always required

B. Only a small amount of catalyst is generally needed, since it is not consumed by the reaction and can be reused

C. Catalysts must be replaced after every single use

D. Catalysts are consumed in stoichiometric amounts, just like reactants

Question 89

If a catalyst lowers a reaction's activation energy from a high value to a much lower value, but the reactants' and products' energy levels remain the same, what happens to the reaction's overall enthalpy change?

A. The enthalpy change decreases significantly

B. The overall enthalpy change remains exactly the same, since only the activation energy (the pathway) has changed, not the reactants' or products' energy levels

C. The enthalpy change increases significantly

D. The reaction becomes endothermic instead of exothermic

Question 90

In the human body, enzymes catalyze biochemical reactions (such as those in digestion) by:

A. Increasing the temperature of the body significantly

B. Lowering the activation energy required for these reactions to proceed at body temperature

C. Consuming themselves permanently in each reaction

D. Preventing any reactions from occurring at all

Question 91

Respiration is best defined as a biochemical process in which:

A. Energy is absorbed and stored as food within a biological system

B. Energy is released from food in a biological system

C. Water is converted into oxygen within a biological system

D. Carbon dioxide is converted into glucose within a biological system

Question 92

Respiration is classified, in terms of energy change, as a(n):

A. Endothermic process

B. Exothermic process

C. Energy-neutral process

D. Non-chemical process

Question 93

Respiration that requires oxygen to break down glucose and release energy is called:

A. Anaerobic respiration

B. Aerobic respiration

C. Photosynthesis

D. Fermentation only

Question 94

Respiration that does not require oxygen to break down glucose and release energy is called:

A. Aerobic respiration

B. Anaerobic respiration

C. Photosynthesis

D. Combustion

Question 95

In aerobic respiration, glucose reacts with oxygen to produce which two main waste products, alongside energy?

A. Lactic acid and water

B. Carbon dioxide and water

C. Carbon dioxide and lactic acid

D. Oxygen and nitrogen

Question 96

In anaerobic respiration, glucose is broken down (without oxygen) to produce which byproduct, alongside energy?

A. Carbon dioxide and water

B. Lactic acid

C. Oxygen gas

D. Glucose itself, unchanged

Question 97

Which type of respiration, aerobic or anaerobic, releases more energy from a given amount of glucose?

A. Anaerobic respiration releases more energy than aerobic respiration

B. Aerobic respiration releases more energy than anaerobic respiration

C. Both release exactly the same amount of energy

D. Neither type of respiration releases any energy

Question 98

Besides being used for building the body, what important additional role do lipids play in relation to energy?

A. Lipids act as reserve (stored) energy sources, capable of storing very large amounts of energy

B. Lipids have no role in energy storage at all

C. Lipids are only used to transport oxygen in the blood

D. Lipids directly convert into lactic acid

Question 99

During intense exercise, when the oxidation of glucose alone is not sufficient to meet the body's energy demands, which substances are oxidized instead to provide additional energy?

A. Proteins exclusively

B. Lipids

C. Water

D. Carbon dioxide

Question 100

Comparing aerobic respiration (glucose + oxygen -> carbon dioxide + water + energy) with anaerobic respiration (glucose -> lactic acid + energy), which equation produces carbon dioxide as a product?

A. Anaerobic respiration only

B. Aerobic respiration only

C. Both aerobic and anaerobic respiration

D. Neither type of respiration

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