Question 1

Which type of reaction is demonstrated by the use of an instant cold pack for sports injuries, as shown in the image?

Accepted Answer

Endothermic reaction

Question 2

What is the primary driving force for chemical reactions according to the study materials?

Accepted Answer

Achieving a lower energy state (greater stability)

Question 3

Which of the following statements best describes an exothermic reaction?

Accepted Answer

Energy is released to the surroundings, causing a heating effect.

Question 4

In terms of bond energetics, which process is always endothermic?

Accepted Answer

Bond breaking

Question 5

A chemical reaction has reactants with higher enthalpy than the products. What is the sign of $$\Delta H$$ for this reaction?

Accepted Answer

$$\Delta H is $$negative

Question 6

Which scenario best illustrates a spontaneous reaction?

Accepted Answer

A reaction that occurs immediately when reactants are mixed, without external energy input

Question 7

Which of the following is true about endothermic reactions?

Accepted Answer

They absorb energy from the surroundings.

Question 8

If a reaction requires more energy to break bonds than is released when new bonds are formed, what type of reaction is it?

Accepted Answer

Endothermic

Question 9

Which equation correctly represents the enthalpy change ($$\Delta H) $$for an exothermic reaction?

Accepted Answer

$$\Delta H = H_{products} - H_{reactants}$$, and $$\Delta H \u003c 0$$

Question 10

A student mixes two chemicals and observes that the container becomes warm. Which statement best explains this observation?

Accepted Answer

The reaction is exothermic and releases heat to the surroundings.

Question 11

Which real-world example best illustrates an endothermic reaction?

Accepted Answer

Using an instant cold pack for a sports injury

Question 12

Why are exothermic reactions more common than endothermic reactions?

Accepted Answer

Exothermic reactions always produce more stable products with lower energy.

Question 13

Which of the following best describes the relationship between stability and energy in chemical reactions?

Accepted Answer

Lower energy states are more stable.

Question 14

During a chemical reaction, which step is always exothermic?

Accepted Answer

Forming new bonds between atoms

Question 15

A reaction has $$\Delta H = +50\ 	ext{kJ}$$ and causes the surroundings to cool down. What type of reaction is this?

Accepted Answer

Endothermic

Question 16

Which of the following is NOT a characteristic of a spontaneous reaction?

Accepted Answer

Requires continuous energy input

Question 17

If a chemical reaction results in products that are less stable (have more energy) than the reactants, what can be inferred about the reaction?

Accepted Answer

It is likely an endothermic reaction

Question 18

Which of the following best explains why cold packs are used for injuries?

Accepted Answer

They absorb heat from the injury site, causing a cooling effect.

Question 19

Which statement about the Second Law of Thermodynamics is correct according to the study materials?

Accepted Answer

Entropy always increases with time.

Question 20

A reaction occurs only after heating the reactants. What is the term for the minimum energy required to start this reaction?

Accepted Answer

Activation energy

Chemical Energetics: Why Reactions Happen

Study Guide - Practice Questions