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Chapter 12
General Chemistry 2 Spring Semester 2026
| Question | Answer |
|---|---|
| What does the rate of a chemical reaction measure? | The rate of a chemical reaction is a measure of how fast the reaction occurs |
| How is the rate of a chemical reaction expressed? | Change in concentration of reactants (-) or products (+) divided by the rate of time |
| What does the term rate refer to in a reaction rate? | The initial rate A chemical with a coefficient of 1 |
| Does the reaction rate change when using reactant or products? | The reaction rate is the same whether we use the reactants or the products |
| What is the reaction rate equation (both reactants and products)? | Reactants: (-1/(coefficient of reactant))(concentration of reactant over time) Products: (1/(coefficient of reactant))(concentration of reactant over time) |
| How are reaction rates reported? | As positive quantities |
| What are the factors affecting reaction rate? | Reactant concentration and temperature |
| What is the Chemist's rule for temperature? | For each 10 degrees Celsius rise in temperature, the rate of the reaction doubles |
| What happens in a reaction when temperature is increased? | The reaction rate increases |
| What happens in a reaction when reactant concentration is raised? | Generally, the higher the concentration of reactants, the faster the reaction Note: if reactants are far apart, they collide less often |
| What is a catalyst? | Substances that affect the rate of a reaction without being consumed |
| What is the rate law (definition)? | The rate of a reaction is directly proportional to the concentration of each reactant raised to a power |
| What is the rate law (equation)? | Rate= k([A]^n)([B]^m) |
| What is k in the rate law? How to determine k? | The rate constant (at a set temperature) that must be experimentally determined |
| What are [A] and [B] in the rate law? | The initial concentrations of A and B |
| What are n and m called? In respect to what? How to determine the variables? | m and n are called the reaction orders with respect to the concentrations of A and B, respectively- must be experimentally determiend |
| When n is zero what is the reaction order? How does the rate relate to the concentration of A? What is the unit of k? What is the rate law? | N=0, the reaction is zero order and the rate is independent of the concentration of A. Rate=k[A]^0= k The unit of k: Ms^-1 |
| When n is 1 what is the reaction order? How does the rate relate to the concentration of A? What is the unit of k? What is the rate law? | N=1, the reaction is first order and the rate is directly proportional to the concentration of A Rate=k[A]^1= k[A] The unit of k: s^-1 |
| When n is 2 what is the reaction order? How does the rate relate to the concentration of A? What is the unit of k? What is the rate law? | N=2, the reaction is second order and the rate is proportional to the square of the concentration of A Rate=k[A]^2 The unit of k: M^-1s^-1 |
| How are rate laws determined? | Experimentally |
| What is reaction order always defined in terms of? | Reactant concentraions |
| What is the order of a reactant not related to? | The stoichiometric coefficient of the reactant in the balanced chemical equation |
| What does the rate law show? | The relationship between the rate of a reaction and the concentrations of the reactants |
| What is the integrated rate law a relationship between? | The integrated rate law for a chemical reaction is a relationship between the concentrations of the reactants and time |
| What is the slope of a zero order reaction? | -k |
| What is the slope of a first order reaction? | -k |
| What is the slope of a second order reaction? | k |
| What does the graph of a zero order reaction show a relationship between? | [A]vs time |
| What does the graph of a first order reaction show a relationship between? | 1/[A]vs time |
| What does the graph of a second order reaction show a relationship between? | ln[A]vs time |
| What is the half-life of a reaction? | The time required for the concentration of a reactant to fall to one-half of its initial value |
| What does the Arrhenius equation show? | The relationship between the rate constant (k) and the temperature in kelvin (T) |
| What is the Arrhenius equation? | k=Ae^(-Ea/RT) |
| What the activated complex (transition state)? (Definition) | A high-energy intermediate state between reactant and product |
| What is activation energy (E sub a)? (Definition) | An energy barrier in a chemical reaction that must be surmounted for the reactants to be converted into products |
| What does the exponential factor represent in the Arrhenius equation? | Represents the fraction of molecules that have enough energy to surmount the activation barrier |
| What causes the exponential factor to increase (e^-E sub a/RT) | T increases or E sub a decreases |
| How does temperature affect the reaction rate? | As temperature increases, the average kinetic energy increases, more reactant molecules overcome the energy barrier, and the rate of reaction increases |
| What is the collision model? | Two molecules react after a sufficiently energetic collision with the correct orientation brings the reacting group together |
| What is another way to write A in the Arrhenius equation? | pze^-E sub a/RT |
| What does p represent in the collision model of kinetics equation? | Orientation factor: the fraction of collisions with an orientation that allows the reaction to occur |
| What does z represent in the collision model of kinetics equation? | Collision frequency: the number of collisions that occur per unit time |
| What is the collision frequency? | The number of collisions that occur per unit time |
| What is the orientation factor? | The fraction of collisions with the proper orientation that allows the reaction to occur |
| What does the overall reaction show? | Overall reaction shows the starting substances and the ending substances |
| How can the overall reaction be broken down? What do they represent | Overall reaction can be broken down into several elementary steps, which represent the actual interaction between the reactant molecules. Cannot be broken down into simpler steps |
| What is the reaction mechanism? | Reaction Mechanism is the series of individual chemical steps by which an overall chemical reaction occurs |
| What is the reaction intermediate? | Reaction intermediate forms in one elementary step and is consumed in another |
| What does show up in the overall reaction (related to reaction mechanism)? | Reaction intermediate |
| What is molecularity? | the number of reactant particles involved in an elementary step |
| What is unimolecular? | one particle; A products |
| What is bimolecular? | two particles (same or different) |
| What is termolecular? | three particles (same or different) |
| What is the rate determining step? | The step in a reaction mechanism that occurs much more slowly than other steps |
| What is a catalyst? | A substance that increases the rate of a chemical reaction but is not consumed by the reaction |
| How does it work? | By providing an alternative mechanism ofr the reaction with a lower activation energy, and therefore a higher reaction rate |
| What is a homogenous catalyst? | The catalyst exists in the same phase (or state) as the reactants |
| What is a heterogenous catalyst? | The catalyst exists in a different phase than the reactants |
| What three conditions must be met to validate a mechanism? | The elementary step must sum to the overall reaction The rate law predicted by the mechanism must be consistent with. the experimentally observed rate law Each elementary step should have an order of three or less |
Created by:
KristenR2025