Chapter 18 Reaction Rates And Equilibrium Part 2 3/13/11

An elementary reaction is a type of reaction in which reactants are directly converted into products in a single step. This means that there are no intermediate steps or complex mechanisms involved. Elementary reactions are often simple and straightforward, involving the collision and rearrangement of atoms or molecules. They are important in understanding reaction kinetics and can be used to determine the rate of a chemical reaction.

The standard entropy of a liquid or solid substance at 25 °C is designated as S exponent 0. This indicates that the substance has a standard entropy value of zero at this temperature. Standard entropy is a measure of the disorder or randomness of a substance, and a value of zero suggests that the substance has no disorder or randomness at 25 °C.

As temperature increases, the movement and energy of particles also increase. This leads to a greater number of possible arrangements or states that the particles can be in. Since entropy is a measure of the number of possible arrangements or states, it tends to increase when temperature increases. Therefore, the correct answer is "increase".

An exothermic reaction releases energy to the surroundings, which is a favorable factor for a spontaneous reaction. Additionally, an increase in entropy indicates an increase in the randomness or disorder of the system, which is also a favorable factor for spontaneity. Therefore, when both factors, exothermicity and increase in entropy, are present in a reaction, it is considered spontaneous.

At 0 K, a perfect crystal is in its most ordered and stable state, with no randomness or disorder. In this state, the entropy is at its minimum value, which is 0. This is because entropy is a measure of the randomness or disorder in a system, and a perfect crystal at absolute zero has no randomness or disorder, resulting in an entropy value of 0.

A one-step reaction is a reaction that occurs with only one activated complex between the reactants and the products. This means that the reaction proceeds directly from the reactants to the products without any intermediate steps or multiple activated complexes.

The Gibbs free-energy change (ΔG) represents the maximum amount of energy available to do useful work in a system. It indicates the potential for a chemical reaction or physical process to perform work. This work can include mechanical work, electrical work, or any other form of useful energy transfer. Therefore, the correct answer for this question is "work."

A reaction progress curve is a graph that shows the energy changes that happen as reactants are transformed into products. It provides a visual representation of the energy profile of a chemical reaction, displaying the energy of the system at different stages of the reaction. By plotting the energy changes on the y-axis and the progress of the reaction on the x-axis, the curve illustrates how the energy of the system fluctuates throughout the reaction process. This allows scientists to analyze and understand the energy changes that take place during the conversion of reactants to products.

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

The equation used to calculate the Gibbs free-energy change is ΔG = ΔH - TΔS, where ΔH represents the change in enthalpy, ΔS represents the change in entropy, and T represents the temperature in kelvins. This equation takes into account the changes in both enthalpy and entropy and their relationship to temperature, allowing for the calculation of the Gibbs free-energy change.

The actual kinetic order of a reaction cannot be determined solely by theoretical calculations or assumptions. It must be determined through experimentation, where the reaction is carried out under controlled conditions and the rate of reaction is measured at different concentrations of reactants. By analyzing the data obtained from these experiments, the actual kinetic order can be determined.

A nonspontaneous reaction is not favored because it has heat changes, entropy changes, or both working against it. This means that the reaction requires an input of energy or a decrease in disorder, making it unlikely to occur spontaneously.

The symbol for entropy is S, and the units for entropy are joules per kelvin (J/K). Entropy is a thermodynamic property that measures the amount of disorder or randomness in a system. It is a state function and is related to the distribution of energy and the number of microstates in a system. The units of joules per kelvin indicate that entropy is measured in terms of energy per unit temperature.

The pressure at S exponent 0 for gaseous substances is 101.3 kPa. This is a commonly used standard pressure value known as 1 atmosphere (atm) or 760 mmHg. It represents the average atmospheric pressure at sea level and is used as a reference point in many scientific calculations and experiments.

In a first-order reaction, 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. The reaction rate is not dependent on the concentration of any other reactants or products present in the reaction.

The size and direction of heat (enthalpy) changes and entropy changes together determine whether a reaction is spontaneous. This means that the amount of heat released or absorbed during a reaction, as well as the change in disorder or randomness of the system, play a role in determining whether the reaction will occur spontaneously. If the enthalpy change is negative (heat is released) and the entropy change is positive (increase in disorder), the reaction is more likely to be spontaneous. Conversely, if the enthalpy change is positive (heat is absorbed) and the entropy change is negative (decrease in disorder), the reaction is less likely to be spontaneous.

The equation used to calculate standard entropy change (triangleS exponent 0) is ΔS0 =S exponent 0 (products) - S exponent 0 (reactants). This equation represents the difference in standard entropy between the products and reactants of a chemical reaction. The standard entropy of a substance is a measure of the disorder or randomness of its particles, and the change in standard entropy reflects the change in disorder during the reaction. By subtracting the standard entropy of the reactants from the standard entropy of the products, we can determine the overall change in entropy for the reaction.

The standard entropy of calcium carbonate (CaCO3) is 88.7 J/K mol. Standard entropy is a measure of the disorder or randomness of a substance at a specific temperature. In this case, the given value represents the standard entropy of one mole of calcium carbonate at a specific temperature.

The specific rate constant (k) for a reaction is a proportionality constant that relates the concentrations of reactants to the rate of the reaction. This means that the rate of the reaction is directly proportional to the concentrations of the reactants raised to some power, as determined by the rate law for the reaction. The specific rate constant is unique for each reaction and is determined experimentally. It represents the speed at which the reaction occurs and is affected by factors such as temperature, presence of a catalyst, and the nature of the reactants.

The order of a reaction refers to the power to which the concentration of a reactant must be raised in order to match the observed relationship between concentration and rate. It helps determine how the rate of the reaction is affected by changes in the concentration of reactants.

In spontaneous processes, the system loses free energy, resulting in a negative value for ΔG. This indicates that the process is energetically favorable and will occur without the need for external work. On the other hand, in nonspontaneous processes, the system requires work to be expended in order to proceed forward under the specified conditions. This results in a positive value for ΔG, indicating that the process is energetically unfavorable and will not occur without external intervention. Therefore, the correct answer is positive, negative.

The equation used to calculate the standard free-energy change (ΔG exponent 0) of a chemical reaction is ΔG exponent 0 = ΔH exponent 0=TΔS0. In this equation, ΔH exponent 0 represents the standard enthalpy change, ΔS exponent 0 represents the standard entropy change, and T represents the temperature in kelvins. This equation allows us to determine the change in free energy for a reaction under standard conditions, where the initial and final states are at a temperature of 298 K and a pressure of 1 atm.

The correct answer states that the standard free-energy change (ΔG exponent 0) of a chemical reaction can be calculated using ΔG exponent 0 f, which represents the standard free-energy change for the formation of substances from their elements. The formula to calculate ΔG0 is ΔG exponent 0 f (products) = ΔG exponent0 f (reactants). This means that by knowing the standard free-energy change for the formation of the reactants and products from their elements, one can determine the standard free-energy change of the overall reaction.

An intermediate product of a reaction refers to a product that is formed during a chemical reaction but is not the final desired product. Instead, it serves as a reactant in a subsequent step or reaction. This means that it undergoes further transformations to eventually yield the desired end product.