QUIZ 4_COLLISION THEORY_MASS REL OF CHEM RXN_H/P CARE PRODUCTS

According to the collision theory, what must happen for a chemical reaction to occur?

• Molecules must absorb thermal energy.

• Molecules, atoms, or ions must first collide.

• Products must be removed immediately from the system.

• Reactants must be in a homogeneous mixture.

Answer explanation

According to collision theory, a chemical reaction occurs when molecules, atoms, or ions collide with sufficient energy and proper orientation. Thus, the correct answer is that they must first collide.

A collision that successfully leads to the formation of products is called a/an:

• Inert collision.

• Unsuccessful collision.

• Effective collision.

• Simple collision.

Answer explanation

An effective collision is one that results in the formation of products during a chemical reaction. In contrast, inert and unsuccessful collisions do not lead to product formation, making effective collision the correct choice.

What is the minimum amount of energy particles must possess for a collision to be successful?

• Heat of fusion.

• Kinetic energy.

• Activation energy.

• Potential energy.

Answer explanation

The minimum energy required for a successful collision is known as activation energy. It is the energy needed to initiate a reaction, allowing particles to overcome barriers and react effectively.

Besides having minimum energy, what other condition is necessary for collisions to become effective collisions?

• The reactants must be concentrated.

• Proper orientation.

• A catalyst must be present.

• Low temperature.

Answer explanation

For collisions to be effective, not only must the reactants have minimum energy, but they also need to be properly oriented. This ensures that the reactive parts of the molecules collide in a way that can lead to a reaction.

The minimum energy requirement that serves as a "threshold/doorstep" for a chemical reaction to occur is called:

• Standard enthalpy.

• Energy of reactants.

• Activation Energy (Ea).

• Bond energy.

Answer explanation

The minimum energy required for a chemical reaction to occur is known as Activation Energy (Ea). It represents the energy barrier that must be overcome for reactants to transform into products.

What is the term for the original substances that are changed into different substances during a chemical reaction?

• Solvents

• Products

• Catalysts

• Reactants

Answer explanation

The term 'reactants' refers to the original substances that undergo change during a chemical reaction, transforming into new substances called products. Therefore, the correct answer is 'reactants'.

Which type of reaction happens when energy is absorbed in the formation of the products?

• Exothermic reaction.

• Isothermic reaction.

• Endothermic (or endergonic) reaction.

• Spontaneous reaction.

Answer explanation

An endothermic (or endergonic) reaction is characterized by the absorption of energy during the formation of products, making it the correct choice. In contrast, exothermic reactions release energy.

In an endothermic reaction, how does the energy of the reactants compare to the energy of the products?

• Energy of reactants is greater than the energy of the products.

• Energy of reactants is less than the energy of the products.

• Energy of reactants is equal to the energy of the products.

• The activation energy is always zero.

Answer explanation

In an endothermic reaction, energy is absorbed from the surroundings, resulting in products that have higher energy than the reactants. Therefore, the energy of the reactants is less than the energy of the products.

Which type of reaction happens when energy is released in the formation of the products?

• A. Endothermic reaction.

• B. Exothermic (or exergonic) reaction.

• C. Neutral reaction.

• D. Catalytic reaction.

Answer explanation

An exothermic (or exergonic) reaction is characterized by the release of energy when products are formed, making it the correct choice. In contrast, endothermic reactions absorb energy.

In an exothermic reaction, how does the energy of the reactants compare to the energy of the products?

• A. Energy of reactants is less than the energy of the products.

• B. Energy of reactants is equal to the energy of the products.

• C. Energy of reactants is greater than the energy of the products.

• D. The difference in energy is the activation energy.

Answer explanation

In an exothermic reaction, the reactants have higher energy than the products. This energy difference is released as heat, making option C correct: Energy of reactants is greater than the energy of the products.