Chemical Kinetics and Chemical Equilibria

Flashcards covering chemical kinetics, collision theory, factors affecting reaction rates, activation energy, the Law of Mass Action, and types of chemical reactions based on the lecture slides.

What is chemical kinetics?

Chemical kinetics is the study of the mechanism by which reactions occur and the rates of those chemical reactions.

How is reaction kinetics defined in the lecture?

Reaction kinetics is the study of the rates of chemical reactions and the factors that influence reaction velocities.

What is meant by the mechanism of a reaction?

It is the sequence of steps by which reactants are converted into products, which may involve intermediate species that are consumed so promptly that they are not observed during the reaction.

How is the rate or speed of a chemical reaction defined?

It is the amount of reactants converted to products in a given unit of time, representing the rate at which reactants are consumed or products are produced.

In what units are reactant amounts and reaction times usually expressed?

Amounts of reactants are usually expressed in moles per liter ($\text{moles/liter}$), while time may be expressed in seconds, minutes, hours, or days depending on whether the reaction is fast or slow.

What are the key conditions required for a reaction to occur according to Collision Theory?

1. Reactant particles must collide with each other. 2. Colliding particles must possess a certain minimum total amount of energy. 3. Reactants must be oriented in a specific way upon collision in some cases.

How do molecular collisions differ between liquid/gaseous states and solid states?

Most reactions are carried out in a gaseous or liquid state where reactants collide throughout the mixture, whereas reactions of solids take place only on the solid surface at first.

What is activation energy?

Activation energy is the minimum kinetic energy reactant particles must possess in order for their collision to result in a chemical reaction.

How does activation energy relate to a slow reaction?

In a slow reaction, the activation energy is far above the average energy content of the reacting particles.

Why might product formation fail even when colliding particles possess sufficient activation energy?

Product formation may still fail if the colliding reactant particles do not have the proper collision orientation.

What four main factors influence reaction rates?

1. Nature of reactants 2. Reaction concentration 3. Reaction temperature 4. Presence of catalyst

Which two categories define the nature of reactants affecting reaction rates?

1. Physical nature (which includes physical state and particle size) 2. Chemical nature.

How does temperature affect the rate of a chemical reaction?

The rate of a chemical reaction doubles for every $10\,^{\circ}\text{C}$ increase in temperature.

What is the sequence of events when reaction temperature is increased?

Increasing temperature $\rightarrow$ increases average kinetic energy $\rightarrow$ leads to more collisions $\rightarrow$ increases rate of reaction.

What is the difference between homogeneous and heterogeneous catalysts?

Homogeneous catalysts are in the same phase as the reactants, whereas heterogeneous catalysts exist in a separate phase from the reactants.

What type of catalysts operate within the human body?

Enzymes.

How does an increase in reactant concentration lead to an increased reaction rate?

Increasing reactant concentration increases the number of particles, which increases the number of effective collisions, thereby increasing the rate of reaction.

What does the Law of Mass Action state?

It states that the rate of a chemical reaction is proportional to the active concentration masses (formula weight concentration) of the reacting substances present at that time.

What is the mathematical equation for reaction rate according to the Law of Mass Action?

$V = K \times A^m \times B^n$, where $V$ is reaction rate, $K$ is proportionality constant, $A$ and $B$ are reactants, and $m$ and $n$ are powers equal to the number of molecules of reactants.

According to the Law of Mass Action equation $V = K \times A^m \times B^n$, what is the reaction rate if $A = 2$, $B = 2$, and $K = 1$ (assuming powers of $1$)?

$$V = 1 \times 2 \times 2 = 4$$

What characterizes a reversible reaction?

Reactions occur in both directions simultaneously ($A + B \rightleftharpoons C + D$), meaning products can react or break down to reform the reactants.

What three manifestations indicate an irreversible reaction?

1. Formation of precipitate 2. Formation of gas 3. Formation of slightly ionized molecules