Question

1.) Examine the scenario.

During a reaction, reactants that are low in energy react and form products that are high in energy. Which answer choice correctly states what must have happened during the reaction, according to the law of conservation of energy?
Energy must have been destroyed during the reaction Energy must have been created during the reaction.
Energy must have been absorbed from the surrounding environment.
Energy must have been released into the surrounding environment.

2.) Examine the false statement.

A reversible reaction contains a forward reaction, which occurs when products form reactants, and a reverse reaction, which occurs when reactants form products.

Select the rewording that makes the statement true.

A reversible reaction contains a reverse reaction, which occurs when reactants form products, and a forward reaction, which occurs when products form reactants.
An equilibrium reaction contains a reverse reaction, which occurs when reactants form products, and a forward reaction, which occurs when products form reactants
An equilibrium reaction contains a forward reaction, which occurs when reactants form products, and a reverse reaction, which occurs when products form reactants.
A reversible reaction contains a forward reaction, which occurs when reactants form products, and a reverse reaction, which occurs when products form reactants.

3.) Examine the reversible reaction among gases.

3H2 + N2 ⇌ 2NH3

If pressure were added to this reaction when it is at chemical equilibrium, what would occur?

The reaction rate of the reverse reaction would decrease in order to decrease the number of particles.
The reaction rate of the reverse reaction would increase in order to decrease the number of particles.
The reaction rate of the forward reaction would increase in order to decrease the number of particles.
The reaction rate of the forward reaction would decrease in order to decrease the number of particles.

4.) Examine the scenario.

Tori is studying a chemical reaction and its reaction rate. After observing the initial rate, she adds thermal energy to the reaction.

Which of the answer choices correctly describes how the addition of thermal energy will affect the reaction rate?

The increase in energy will cause the reactants' particles to move slower, which will decrease their temperature and lead to a slower reaction rate.
The increase in energy will cause the reactants' particles to move faster, which will increase their temperature and lead to a faster reaction rate.
The increase in energy will cause the reactants' particles to move faster, which will decrease their temperature and lead to a faster reaction rate.
The increase in energy will cause the reactants' particles to move slower, which will decrease their temperature and lead to a faster reaction rate.
The increase in energy will cause the reactants' particles to move faster, which will increase their temperature and lead to a slower reaction rate.

5.) Which of the answer choices correctly describes Le Châtlier's principle?

When a reaction is at chemical equilibrium, a change in the system will cause the system to become an irreversible reaction and become unable to regain chemical equilibrium.
When a reaction is at chemical equilibrium, a change in the system will cause the system to shift in the direction that will balance the change and help the reaction regain chemical equilibrium.
When a reaction is at chemical equilibrium, a change in the system will cause the system to shift in the direction that will increase the change's effect and keep the reaction from regaining chemical equilibrium.
When a reaction is at chemical equilibrium, a change in the system will cause the system to become an irreversible reaction until it regains chemical equilibrium.

Answer 1

1) The answer is: Energy must have been absorbed from the surrounding environment.

There are two types of reaction:

1) Endothermic reaction (ΔH > 0, chemical reaction that absorbs more energy than it releases). In endothermic reactions heat is reactant.

Because products have higher energy, this example is endothermic reaction.

2) Exothermic reaction (chemical reaction that releases more energy than it absorbs).

2) The answer is: A reversible reaction contains a forward reaction, which occurs when reactants form products, and a reverse reaction, which occurs when products form reactants.

For example, balanced reversible chemical reaction: N₂ + 3H₂ ⇄ 2NH₃.

Nitrogen and hydrogen are reactants and ammonia is product of reaction. Reaction goes in both direction. Ammonia is synthesized from nitrogen and hydrogen and ammonia decomposes on nitrogen and hydrogen.

The amount of substance of reactants and products of reaction do not change when chemical reaction is in chemical equilibrium.

In a chemical reaction, chemical equilibrium is the state in which both reactants and products are present in concentrations which not change with time. Speed of direct and irreversible chemical reaction are equal

3) The answer is: The reaction rate of the forward reaction would increase in order to decrease the number of particles.

According to Le Chatelier's Principle the position of equilibrium moves to counteract the change.

The equilibrium shift to the right, so more product (ammonia) will be produced.

There are less molecules of ammonia than molecules of hydrogen and nitrogen. For every two molecules of ammonia, there are four molecules of hydrogen and nitrogen.

4) The answer is: The increase in energy will cause the reactants' particles to move faster, which will increase their temperature and lead to a faster reaction rate.

The reaction rate is the speed at which reactants are converted into products.

The collision theory states that a certain fraction of the collisions (successful collisions) cause significant chemical change.

The successful collisions must have enough energy (activation energy).

Chemical bonds are broken and new bonds are formed.

Particles are in constant, random motion and possess kinetic energy, molecules faster and have more collisions.

5) The answer is: When a reaction is at chemical equilibrium, a change in the system will cause the system to shift in the direction that will balance the change and help the reaction regain chemical equilibrium.

For example, chemical reaction: heat + NH₄⁺ + OH⁻ ⇄ NH₃ + H₂O.

According to Le Chatelier's Principle, the position of equilibrium moves to counteract the change, because heat is increased, system consume that heat, so equilibrium is shifted to right, by decreasing concentration of reactants and increasing concentration of product.