Chapter 18 Chemistry: Reaction Rates Questions

The common ion effect refers to the decrease in solubility of an ionic compound when a common ion is added to the solution. This occurs because the presence of the common ion reduces the concentration of the dissolved ions, shifting the equilibrium towards the formation of the solid precipitate. The common ion effect is a consequence of Le Chatelier's principle, which states that a system at equilibrium will shift in a way that counteracts any imposed changes. In this case, the addition of the common ion disrupts the equilibrium, causing the solubility of the compound to decrease.

Free energy refers to the energy that is available to do work. It is a thermodynamic concept that measures the maximum amount of work that can be extracted from a system. In chemical reactions, the change in free energy determines whether the reaction is spontaneous or non-spontaneous. If the change in free energy is negative, the reaction is spontaneous and can proceed on its own. On the other hand, if the change in free energy is positive, the reaction is non-spontaneous and requires an input of energy to occur. Therefore, free energy is a crucial factor in understanding the thermodynamics and feasibility of chemical reactions.

A common ion refers to an ion that is present in both salts of a solution. When two salts containing a common ion are dissolved in water, the common ion will affect the solubility of the salts. According to the common ion effect, the presence of a common ion will decrease the solubility of a salt in a solution, as the equilibrium shifts towards the formation of a precipitate. This is due to the principle of Le Chatelier, which states that a system will shift to counteract any change imposed upon it. In the case of a common ion, the increased concentration of the common ion causes the system to shift towards the formation of a precipitate to reduce the concentration of the ion.

The correct answer is "activated complex". An activated complex refers to an unstable arrangement of atoms that forms momentarily at the peak of the activation-energy barrier during a chemical reaction. It is a transitional state between the reactants and the products, and it represents the highest energy point in the reaction pathway. The formation of the activated complex is a crucial step in determining the rate of a reaction.

The correct answer is "rate". Rate is a measure of the speed at which a change occurs within a given interval of time. It is used to describe how quickly a reaction takes place or how fast a process occurs. The rate of a reaction can be influenced by factors such as temperature, concentration, and catalysts.

A first-order reaction is a reaction in which the reaction rate is directly proportional to the concentration of only one reactant. This means that as the concentration of the reactant increases, the reaction rate also increases proportionally. The rate law for a first-order reaction can be expressed as rate = k[A], where [A] is the concentration of the reactant and k is the specific rate constant. This type of reaction is commonly observed in radioactive decay and certain chemical reactions where the concentration of one reactant is much higher than the others.

The collision theory explains that atoms, ions, and molecules can react to form products when they collide with one another. However, for a reaction to occur, the colliding particles must have enough kinetic energy. This theory helps to understand the factors that affect the rate of a chemical reaction, such as temperature, concentration, and surface area. It also provides insights into the concept of activation energy, which is the minimum energy required for a reaction to occur. Overall, the collision theory is a fundamental concept in chemistry that explains how reactions take place at the molecular level.

Activation energy is the minimum energy that colliding particles must have in order to react. It is the energy barrier that must be overcome for a chemical reaction to occur. Only particles with enough energy to surpass this barrier can react and form new products. The activation energy is a crucial factor in determining the rate of a reaction, as it influences the number of particles that possess enough energy to react.

An inhibitor is a substance that interferes with the action of a catalyst. It slows down or prevents the catalytic reaction from occurring, reducing the rate of the reaction. Inhibitors can bind to the catalyst and block its active site, preventing the substrate from binding and reacting. They can also alter the conformation of the catalyst, making it less effective in catalyzing the reaction. Overall, inhibitors negatively impact the catalytic activity of a substance and inhibit the reaction from proceeding at its normal rate.

Le Chatelier's principle states that when a stress is applied to a system in dynamic equilibrium, the system will shift in a way that counteracts the stress and restores equilibrium. This means that if a stress, such as a change in temperature, pressure, or concentration, is applied to a system, the system will respond by shifting its reaction to either the left or the right in order to relieve the stress and maintain equilibrium. This principle helps explain how systems respond and adjust to changes in their environment.

A non-spontaneous reaction refers to a reaction that does not occur naturally or spontaneously under the given conditions. It requires an input of energy to proceed in the forward direction. In other words, the reaction does not favor the formation of products and will only occur if energy is supplied to drive the reaction. This can be due to a high activation energy barrier or unfavorable thermodynamic conditions.

A reversible reaction is a reaction in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously. This means that the reaction can proceed in both the forward and reverse directions. In a reversible reaction, the reactants and products are in dynamic equilibrium, meaning that the concentrations of reactants and products remain constant over time. The reaction can be influenced by factors such as temperature, pressure, and concentration, which can shift the equilibrium position towards the reactants or products.

The equilibrium constant is a measure of the extent to which a reaction proceeds to reach equilibrium. It is defined as the ratio of the product concentrations to the reactant concentrations, with each concentration raised to a power equal to the number of moles of that substance in the balanced chemical equation. The equilibrium constant provides information about the position of the equilibrium and whether the reaction favors products or reactants. It is a fundamental concept in chemical equilibrium and is used to calculate equilibrium concentrations and predict the direction of a reaction.

A spontaneous reaction is one that occurs naturally and favors the formation of products at the specified conditions. It does not require any external influence or input of energy to proceed. The reaction will proceed in the direction that leads to a decrease in free energy, resulting in the formation of products.

Entropy is a measure of the disorder or randomness in a system. It is a thermodynamic property that quantifies the number of ways in which a system can be arranged or distributed. In simpler terms, entropy measures the level of chaos or randomness in a system. An increase in entropy indicates a higher degree of disorder, while a decrease in entropy indicates a more ordered state. In the context of the given options, entropy is the only one that directly relates to the concept of disorder in a system.

A transition state is a term sometimes used to refer to an activated complex. It is a high-energy, short-lived species that forms during a chemical reaction. It represents the highest energy point along the reaction pathway and is a critical intermediate between reactants and products. The transition state is characterized by partial bonds and distorted molecular geometry. It is formed when the reactant molecules collide with sufficient energy to overcome the activation energy barrier.

Chemical equilibrium refers to a state of balance in a chemical reaction where the rates of the forward and reverse reactions are equal. In this state, the concentrations of the reactants and products remain constant over time. It is a dynamic process where reactions are still occurring, but there is no net change in the overall concentrations. The concept of chemical equilibrium is important in understanding the behavior of reversible reactions and predicting the concentrations of reactants and products at equilibrium.

The equilibrium position refers to the relative concentrations of reactants and products of a reaction that has reached equilibrium. At equilibrium, the forward and reverse reactions occur at equal rates, resulting in a stable concentration of reactants and products. The equilibrium position can be influenced by factors such as temperature, pressure, and the presence of catalysts.

The law of disorder, also known as the second law of thermodynamics, states that the natural tendency of systems is to move towards maximum disorder or randomness. This means that in any spontaneous process, the overall entropy of the system and its surroundings increases. In the context of the given question, the law of disorder explains why systems tend to move towards maximum randomness, which is the opposite of order.

The rate law is an expression that relates the rate of a reaction to the concentrations of the reactants. It shows how the rate of a reaction depends on the concentrations of the reactants and any other factors that may influence the reaction rate. The rate law equation is determined experimentally and can provide valuable information about the reaction mechanism and the order of the reaction with respect to each reactant.

An elementary reaction is a reaction that occurs in a single step, where reactants are directly converted to products. It is a simple and straightforward reaction mechanism without any intermediate steps or complex reaction pathways. In contrast, a reaction mechanism consists of a series of elementary reactions that occur in multiple steps. Therefore, the given answer correctly describes a reaction in which reactants are converted to products in a single step.

A reaction mechanism refers to the series of elementary reactions or steps that occur during the course of a complex reaction. It provides a detailed understanding of how reactants are transformed into products and the intermediates that are formed along the way. By studying the reaction mechanism, scientists can determine the rate of the reaction, the activation energy required, and the overall energy changes involved. The reaction mechanism is crucial in understanding and predicting the behavior of chemical reactions.

The Gibbs free-energy change is the maximum amount of energy that can be coupled to another process to do useful work. It represents the balance between the enthalpy and entropy changes of a reaction, and determines whether a reaction is spontaneous or non-spontaneous. A negative Gibbs free-energy change indicates a spontaneous reaction, while a positive value indicates a non-spontaneous reaction. The magnitude of the Gibbs free-energy change also determines the extent to which a reaction will proceed towards equilibrium.

The specific rate constant is a proportionality constant that relates the concentrations of reactants to the rate of the reaction. It is a key parameter in the rate law equation, which describes the relationship between the concentrations of reactants and the rate of the reaction. The specific rate constant is influenced by factors such as temperature, activation energy, and the presence of catalysts. It represents the rate at which the reaction proceeds per unit time and is determined experimentally. A higher specific rate constant indicates a faster reaction rate, while a lower specific rate constant indicates a slower reaction rate.

An intermediate is a product of one of the steps in the reaction. It is formed in one step and consumed in a later step, and it is not present in the overall reaction equation. Intermediates are formed during the reaction but are not present in the final products. They are often unstable and can react further to form the desired products.

The solubility product constant is a measure of the extent to which a solid substance will dissolve in water. It is calculated by multiplying the concentrations of the ions in the solution, with each concentration raised to the power of its coefficient in the dissociation equation. This is because the solubility product constant is based on the equilibrium between the dissolved ions and the solid substance. By multiplying the concentrations of the ions, we can determine the equilibrium position and the extent of dissolution.