13C Reassessment Assignment

The potential energy of the activated complex is equal to area.

• A) 3

• B) 3+4

• C) 1+2

• D) 1

Answer explanation

The potential energy of the activated complex can be represented as the sum of areas 1 and 2, making option C) 1+2 the correct choice. This indicates that the total area corresponds to the potential energy.

The reaction of A + B → C + D is.

• A) exothermic because it releases energy

• B) exothermic because it absorbs energy

• C) endothermic because it absorbs energy

• D) endothermic because it releases energy

Answer explanation

The reaction A + B → C + D is exothermic because it releases energy. This means that the products (C and D) have lower energy than the reactants (A and B), resulting in a net release of energy.

Interval B represents the.

• activation energy

• reaction progress

• potential energy

• transition state

Answer explanation

Interval B represents the activation energy, which is the minimum energy required for a reaction to occur. It is the energy barrier that must be overcome for reactants to transform into products.

Which diagram represents the potential energy of an exothermic reaction?

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• A. The reaction involves only gaseous reactants and products.

• B. The reaction products are carbon dioxide and water.

• C. The reaction releases heat as it proceeds.

• D. The reaction absorbs heat as it proceeds.

Answer explanation

This reaction is classified as exothermic because it releases heat as it proceeds, making option C the correct choice. The combustion of methane produces energy, which is characteristic of exothermic reactions.

What occurs when an atom of chlorine and an atom of hydrogen become a molecule of hydrogen chloride?

• A chemical bond is broken and energy is released.

• A chemical bond is formed and energy is released.

• A chemical bond is broken and energy is absorbed.

• A chemical bond is formed and energy is absorbed.

Answer explanation

When chlorine and hydrogen atoms combine to form hydrogen chloride, a chemical bond is formed. This process releases energy, making the correct choice: 'A chemical bond is formed and energy is released.'

When an exothermic reaction occurs in a water solution, the temperature of the solution

• increases

• decreases

• remains the same

• fluctuates

Answer explanation

In an exothermic reaction, energy is released, usually in the form of heat, which increases the temperature of the surrounding water solution.

A student observed that when sodium hydroxide was dissolved in water, the temperature of the water increased. The student should conclude that the dissolving of sodium hydroxide

• produces a salt solution

• is endothermic

• produces an acid solution

• is exothermic

Answer explanation

The increase in temperature indicates that heat is released during the dissolving process. This means the dissolving of sodium hydroxide is exothermic, as it releases energy to the surroundings.

Activation energy is

• the energy required to form the activated complex.

• the net energy required to turn reactants into products.

• the heat of reaction.

• free energy.

Answer explanation

Activation energy is the energy required to form the activated complex, which is a temporary state during a reaction. This choice correctly defines activation energy, unlike the other options.

For the forward reaction of A+B → C + D, which statement correctly describes the energy changes that occur?

• ΔH= +25. kJ and the reaction is endothermic.

• ΔH= -25. kJ and the reaction is exothermic.

• ΔH= +40. kJ and the reaction is exothermic.

• ΔH= +15. kJ and the reaction is exothermic.

Answer explanation

The correct choice is ΔH= -25. kJ, indicating that the reaction releases energy, making it exothermic. An exothermic reaction has a negative ΔH, while a positive ΔH indicates an endothermic reaction.