AP Chem Unit 9: Thermodynamics and Electrochemistry

_______ is the heat absorbed or released by a system during a constant-pressure process.

Enthalpy

________ is a measure of the randomness in a system.

Entropy

What does thermodynamically favorable mean?

Spontaneuous

TRUE OR FALSE: Temperature and pressure can affect spontaneity.

True

𝜟S means

Entropy (final-initial)

The entropy of the universe ______ in any spontaneous processes.

increases

Entropy increases with the ______ of motion of molecules.

freedom

Entropy of a system increases for processes where:

• gases form from either solids or liquids.

• liquids or solutions form from solids.

• the number of gas molecules increases during a chemical reaction.

The entropy of a pure crystalline substance at absolute zero is

0

What are the factors that increase entropy?

• an increase in volume (more possible positions).

• an increase in temperature (greater distribution of molecular speed).

• an increase in the number of atoms/molecules (more degrees of freedom). 

If 𝜟G is negative, then the forward reaction is _____

spontaneous

If 𝜟G is 0, the system is…

at equilibrium

If 𝜟G is positive, then the reaction is ________ , but spontaneous in the _____ direction

nonspontaneous; reverse

In this equation, how is Q calculated?

[products]/[reactants]

If Q = K, the equilibrium constant, then…

the reaction is at equilibrium

If Q < K, the equilibrium constant, then

the reaction shifts right to form products

If Q > K, the equilibrium constant, then

the reaction shifts left to form reactants

What does thermodynamically favored mean?

It means the reaction is spontaneous and that the products are favored at equilibrium.

What does thermodynamically favored mean in terms of Gibbs and the equilibrium constant (K)?

𝛥G < 0, K > 1

Electrochemistry is the study of the relationships between _____ and ______ ______. It includes the study of both spontaneous and nonspontaneous processes.

electricity; chemical reactions

What is a voltaic (galvanic) cell?

an electrochemical cell in which an electric current is generated from spontaneous oxidation–reduction reactions

What is an electrolytic cell?

The electrolytic cell has an anode (positive) and a cathode (negative) connected to a voltage source. The electrons flow from the anode to the cathode via the voltage source. Allows nonspontaneous reactions to occur.

What is the Nernst equation used for?

Finding cell potential under nonstandard conditions

Spontaneous redox reactions produce a _____ cell potential, or electromotive force.

positive

The more positive the value of the E°_red the greater the tendency for _____ under standard conditions

reduction

The more negative the value of the E°_red the greater the tendency for _____ under standard conditions

oxidation

What is E°_red?

Standard reduction potential