Chemistry Lecture Notes: Kinetics, Equilibrium, and Thermodynamics

A comprehensive set of practice flashcards covering reaction kinetics, equilibrium requirements, Le Chatelier's Principle, entropy, and enthalpy based on lecture notes.

What three conditions are necessary for a reaction to occur according to Collision Theory?

Particles must have enough energy, collide with the proper arrangement (orientation), and the correct particles must collide.

How does an increase in temperature typically affect the rate of a chemical reaction?

It speeds up the action of particles, leading to more collisions and a faster reaction.

Which factors besides temperature affect the rate of a reaction?

Pressure (for gases only), surface area (breaking into pieces increases rate), concentration (higher concentration leads to more collisions), and the nature of the reactants (more or stronger bonds lead to slower reactions).

What is the function of a catalyst in a reaction?

A catalyst is a substance that increases the rate of reaction by lowering the activation energy ($E_a$).

What does a catalyst NOT do in a system at equilibrium?

It does not shift the equilibrium position.

What are the requirements for a system to reach Chemical Equilibrium?

The reaction must be reversible and occur in a closed system where reactants and products can form.

What is the primary characteristic of a system at equilibrium?

The forward and reverse reaction rates are equal, and the concentrations of reactants and products remain constant.

State Le Chatelier's Principle.

When a system at equilibrium is disturbed, the system reacts to reduce the disturbance.

How does an increase in concentration of a substance affect equilibrium?

The reaction will shift away from the side where the substance was added.

In the reaction $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) + \text{Heat}$, what happens if heat is added?

The reaction shifts to the left, favoring the production of reactants.

How does a change in pressure affect a gaseous equilibrium system?

An increase in pressure shifts the reaction toward the side with the fewest moles of gas; a decrease in pressure shifts it toward the side with the most moles of gas.

What happens to the reaction $2NO (g) \rightleftharpoons N_2 (g) + O_2 (g) + 21.6 kcal/mol$ if temperature is increased?

The reaction will shift to the left toward the reactants.

What is Entropy ($S$)?

The disorder of a system or the randomness of molecules.

List the phases of matter in order of increasing entropy.

Solid ($s$) < Liquid ($l$) < Gas ($g$).

Which two tendencies do systems in nature prefer?

Minimum energy (enthalpy) and maximum disorder (entropy).

How is the heat of reaction ($AH$) calculated?

It is the difference between the potential energy of the products and the potential energy of the reactants ($AH = PE_{\text{products}} - PE_{\text{reactants}}$).

What indicates that a reaction is exothermic?

A negative change in enthalpy ($-AH$) and energy of the products being lower than the reactants; heat is released to the surroundings.

What indicates that a reaction is endothermic?

A positive change in enthalpy ($+AH$) and energy of the products being higher than the reactants; the system gains heat from the surroundings.

What is the definition of Activation Energy?

The energy required to get from the reactants to the top of the energy barrier (the "hill") to start the reaction.

In the reaction $H_2O (1) + 285.8 kJ \rightarrow H_2 (g) + O_2 (g)$, what is the $AH$ value?

$AH = +285.8 kJ/mol$, indicating the reaction is endothermic.