Chapter 18 Reaction Rates And Equilibrium

In a typical reaction, as time passes, the amount of reactant decreases and the amount of product increases. This is because reactants are consumed during the reaction to form products.

Increasing the temperature of a chemical reaction increases the kinetic energy of the particles involved. This increase in kinetic energy leads to a higher number of particles having enough energy to overcome the activation energy barrier and react when they collide. Therefore, increasing the temperature increases the number of particles that have enough kinetic energy to react, resulting in an increase in the reaction rate.

When you remove a product, the reaction is pulled in the direction of reactants. This is because by removing a product, the equilibrium of the reaction is disturbed and the system tries to restore the balance by producing more reactants. This is known as Le Chatelier's principle, which states that a system at equilibrium will respond to any changes by shifting in a direction that minimizes the effect of the change.

When the temperature of a chemical reaction increases, it provides more energy to the reactant molecules, allowing them to overcome the activation energy barrier more easily. This leads to an increase in the rate of the forward reaction. According to Le Chatelier's principle, if the forward reaction is exothermic (releases heat), increasing the temperature will cause the equilibrium position to shift in the direction that absorbs heat. Therefore, increasing the temperature of a chemical reaction causes the equilibrium position to shift in the direction that absorbs heat.

A value of Keq less than 1 means that the concentration of reactants is higher than the concentration of products at equilibrium. This indicates that the reaction is favoring the formation of reactants over products, suggesting that the reaction is more likely to proceed in the reverse direction.

Collision theory states that for atoms, ions, or molecules to react and form products when they collide, they must possess sufficient kinetic energy. This energy enables the particles to overcome any activation energy barrier and initiate a chemical reaction. The collision theory emphasizes the importance of both the frequency and energy of collisions in determining the rate of a chemical reaction. Without enough kinetic energy, the particles will not have the necessary energy to break bonds and form new ones, preventing the formation of products.

By dissolving the solid, it breaks down into smaller particles, increasing the surface area available for reaction. Grinding the solid into a fine powder also achieves the same result by breaking it down into smaller particles, thereby increasing the surface area. Both methods enhance the contact between the solid reactant and other reactants, promoting more efficient and faster reactions.

A value of Keq greater than 1 means that the equilibrium position of the reaction lies more towards the products side than the reactants side. This indicates that the forward reaction is favored and the concentration of products is higher compared to the concentration of reactants at equilibrium.

The smaller the particle size, the larger the surface area of a given mass of a particle. This is because as the particle size decreases, the total surface area of the particles increases due to the increased number of particles. Therefore, for a fixed mass of particles, the smaller particle size will have a larger surface area compared to larger particle sizes.

In chemical equilibrium, the rates of the forward and reverse reactions are equal. This means that the rate at which reactants are being converted into products is the same as the rate at which products are being converted back into reactants. As a result, there is no net change in the amount of reactants and products in the chemical system.

The value of Keq for a reaction depends on the temperature. This is because temperature affects the equilibrium constant by altering the rate of the forward and reverse reactions. According to Le Chatelier's principle, an increase in temperature favors the endothermic reaction, while a decrease in temperature favors the exothermic reaction. As a result, the equilibrium position and the value of Keq are influenced by the temperature.

The minimum amount of energy that particles must have in order to react is called activation energy. Activation energy is the energy required for a chemical reaction to occur. It is the energy barrier that must be overcome for reactant particles to transform into product particles.

The rate of chemical reactions can be influenced by several factors, including temperature, concentration, and particle size. Increasing the temperature generally leads to an increase in the rate of reaction as it provides more energy for the particles to collide and react. Higher concentration of reactants also increases the rate of reaction as it increases the frequency of collisions between particles. Particle size can also affect the rate of reaction, with smaller particles having a larger surface area available for collisions and therefore leading to a faster reaction.

Le Châtelier’s principle states that when a system in dynamic equilibrium is subjected to a stress, it will respond by shifting its equilibrium position in a way that minimizes the effect of the stress. This means that if a stress is applied to the system, such as a change in temperature, pressure, or concentration, the system will adjust its reaction rates or concentrations of reactants and products to restore equilibrium and relieve the stress. Therefore, the correct answer is that the system changes to relieve the stress.

When more reacting particles are put into a fixed volume, the concentration of reactants increases. This means that there are more particles available for collisions to occur. With an increase in collision frequency, there is a higher chance of successful collisions between reactant particles, leading to an increase in the reaction rate. Therefore, the correct answer is that the concentration of reactants increases, the collision frequency increases, and, therefore, the reaction rate increases.

When you add a product to a reversible chemical reaction, the reaction is always pushed in the direction of reactants. This is because according to Le Chatelier's principle, when a substance is added to a reaction, the system will shift in the direction that reduces the concentration of that substance. In this case, adding more product will cause the reaction to shift towards the reactants in order to restore equilibrium and reduce the concentration of the added product.

The square brackets in the equilibrium-constant expression indicate the concentrations of substances in moles per liter (mol/L).

A catalyst is a substance that increases the rate of a reaction without being used up itself during the reaction. It achieves this by providing an alternative pathway for the reaction to occur with lower activation energy. This allows the reactants to more easily overcome the energy barrier and form products. The catalyst remains unchanged at the end of the reaction and can be used in multiple reaction cycles.

The equilibrium position of a reaction is determined by the relative concentrations of the system's components at equilibrium. This means that the amounts of reactants and products present in the reaction mixture at equilibrium will determine the position of the equilibrium. If the concentration of reactants is higher, the equilibrium will shift towards the formation of more products, and vice versa. Therefore, concentration plays a crucial role in determining the equilibrium position of a reaction.

Free energy refers to the energy that is available to perform work. In other words, it is the energy that can be used to accomplish tasks or exert force. Therefore, the correct answer is "work".

When particles collide but lack the necessary kinetic energy to react, they do not undergo any chemical changes. This means that their composition remains the same, and they bounce apart without any alteration in their structure or properties. Therefore, the correct answer is "unchanged."

An activated complex is called the transition state because it is unstable and has a high energy level. It represents the point in a chemical reaction where the reactants have absorbed enough energy to reach a state where they can either form products or revert back to reactants. This state is transient and short-lived, hence the term "transition state". The high energy level of the activated complex allows for the breaking and forming of chemical bonds, leading to the formation of products or the reformation of reactants.

An inhibitor is a substance that interferes with the action of a catalyst. It works by binding to the catalyst and preventing it from carrying out its normal function of speeding up a chemical reaction. This inhibition can occur through various mechanisms, such as blocking the active site of the catalyst or altering its structure. By inhibiting the catalyst, the inhibitor slows down or prevents the reaction from occurring, ultimately affecting the overall rate of the reaction.

An increase in pressure causes the system to shift in the direction that reduces the number of gas molecules. This is because increasing the pressure of a gas system will cause the volume to decrease, which will result in an increase in the concentration of the gas molecules. To counteract this increase in concentration, the system will shift in the direction that produces fewer gas molecules, leading to the formation of a smaller volume of gas.

An activated complex is the arrangement of atoms at the peak of the activation-energy barrier. This refers to the transitional state that molecules go through during a chemical reaction when they have absorbed enough energy to overcome the energy barrier. At this point, the reactants are in an unstable state and can either proceed to form products or revert back to the original reactants. Therefore, the correct answer is "peak" as it represents the highest energy point in the reaction pathway.

The given answer suggests that at equilibrium, there are three types of molecules present. However, without further context or information, it is difficult to determine the specific types of molecules being referred to in this question. It is important to note that equilibrium refers to a state of balance where the rate of the forward reaction is equal to the rate of the reverse reaction.

The correct answer is concentration, pressure, and temperature. Stresses that upset the equilibrium of a chemical system refer to factors that disrupt the balance between reactants and products. Concentration refers to the amount of a substance present, pressure refers to the force exerted on the system, and temperature refers to the degree of heat. Changes in any of these factors can affect the equilibrium of a chemical system and shift the reaction towards the formation of more reactants or products.

A catalyst lowers the activation energy, allowing reactions to proceed at a lower energy than is normally required.

Reactions can be classified as spontaneous or nonspontaneous based on the conditions under which they occur. A nonspontaneous reaction is one that does not occur naturally and requires an input of energy to proceed. However, it is possible for a nonspontaneous reaction to become spontaneous under different conditions, such as a change in temperature, pressure, or concentration of reactants. Therefore, some reactions that are nonspontaneous at one set of conditions may become spontaneous at other conditions.

In reversible reactions, two opposite reactions occur simultaneously. This means that the reactants can form products, but at the same time, the products can also react to form the original reactants. The reaction can proceed in both forward and backward directions, resulting in a dynamic equilibrium where the concentrations of reactants and products remain constant over time. This allows for the possibility of the reaction being reversible and able to shift in either direction depending on the conditions.

The activated complex is a short-lived intermediate state that occurs during a chemical reaction. It is formed when reactant molecules collide with enough energy to overcome the activation energy barrier. The lifetime of an activated complex is typically very short, on the order of 10–13 seconds. During this time, the reactant molecules rearrange their bonds to form the products of the reaction. Therefore, the term "10–13 s" best describes the lifetime of an activated complex.

Heat is the factor that helps determine whether a physical or chemical process is spontaneous. Heat is a form of energy that can cause molecules to move faster and increase the likelihood of a reaction occurring. In spontaneous processes, heat is often released or absorbed to drive the reaction forward. Therefore, the presence or absence of heat can play a crucial role in determining the spontaneity of a process.

In chemical reactions where the total number of product molecules is greater than the total number of reactant molecules, entropy tends to increase. This is because the increase in the number of product molecules leads to an increase in the number of possible arrangements or configurations of the particles, resulting in a higher level of disorder or randomness. As entropy is a measure of the disorder or randomness of a system, an increase in the number of possible arrangements corresponds to an increase in entropy.

Spontaneous reactions are reactions that occur naturally and favor the formation of products at the specified conditions. In other words, these reactions proceed in a way that results in the formation of more products than reactants. This can be due to factors such as a decrease in energy or an increase in entropy. Therefore, the correct answer is "products" as they are the desired outcome of spontaneous reactions.

The exponents in the equilibrium-constant expression are the coefficients from the balanced chemical equation. In a balanced chemical equation, the coefficients represent the number of moles of each reactant and product involved in the reaction. These coefficients are used to determine the stoichiometry of the reaction and are crucial in calculating the equilibrium constant. Therefore, the exponents in the equilibrium-constant expression are based on the coefficients from the balanced chemical equation.

The law of disorder states that processes move in the direction of maximum disorder or randomness. This means that as time goes on, systems tend to become more disordered or chaotic. This is also known as the second law of thermodynamics, which states that the entropy of an isolated system will always increase over time. In other words, the natural tendency of systems is to move towards a state of maximum randomness or disorder.

Rates of chemical change are typically expressed as the amount of reactant changing per unit time because it provides a measure of how quickly the reactants are being consumed or converted into products. This helps to quantify the speed at which a chemical reaction is occurring.

In the context of the given question, the statement "No" is the correct answer. This is because it is not possible for any process to be made 100% efficient. Efficiency refers to the ability to perform a task with minimum wasted effort or resources. However, in reality, there are always some inefficiencies or losses that occur in any process due to various factors such as friction, heat dissipation, or other forms of energy loss. Therefore, it is not possible for any process to achieve absolute 100% efficiency.

The correct answer is products. In a chemical reaction, the reactants undergo a transformation to form products. During this transformation, energy is either released or absorbed. The products of a reaction generally have a lower energy state compared to the reactants, as energy is often released in the form of heat or light. Therefore, the arrangement of atoms in the products has the least amount of energy.

Entropy is a measure of the disorder or randomness in a system. It quantifies the number of possible arrangements or states that a system can have. A system with high entropy is considered to be more disordered, while a system with low entropy is more ordered. In thermodynamics, entropy is often associated with the dispersal of energy and the tendency of a system to move towards equilibrium.

In a chemical equation, catalysts are not consumed or chemically altered during a reaction. To show this, the catalyst is often written above the yield arrow in the equation. This indicates that the catalyst is present throughout the reaction and is not used up or changed in any way.

The equilibrium constant (Keq) is the ratio of product concentrations to reactant concentrations at equilibrium, with each concentration raised to a power equal to the number of moles of that substance in the balanced chemical equation.