CHEM111 Thermodynamics II

Flashcards about Thermodynamics II lecture notes.

What is the central focus of the first foray into thermodynamics, often used in the form DUsys = qsys + wsys?

The first law of thermodynamics

What does the second law of thermodynamics determine regarding a process?

Whether or not something will happen and to what extent.

What is a spontaneous process?

A process that occurs naturally once started without any outside intervention.

What is a nonspontaneous process?

A process that does not occur naturally and only occurs with outside intervention.

What thermodynamic quantity dictates spontaneity?

Entropy

What is entropy (S)?

The thermodynamic measure of the randomness, or disorder, of a system.

State the second law of thermodynamics.

The total entropy of the universe increases in a spontaneous process and remains unchanged in a process at equilibrium

What equation is used to calculate the entropy change of a phase change at constant pressure?

ΔS = ΔH/T

What is the standard entropy, S°298, of a substance?

The molar entropy at 298 K and 1 bar pressure.

State the third law of thermodynamics.

The entropy of a perfect crystal at zero kelvin is zero.

How is the entropy of the surroundings (DSsurr) affected by an exothermic process?

DSsurr > 0, as heat is transferred to the surroundings, increasing their disorder.

How is the entropy of the surroundings (DSsurr) affected by an endothermic process?

DSsurr < 0, as heat is absorbed from the surroundings, decreasing their disorder.

What is Gibbs Energy?

G = H - TS

How can the second law of thermodynamics be expressed using Gibbs energy?

DGsys < 0 for a spontaneous process; DGsys = 0 for a process at equilibrium; DGsys > 0 for a nonspontaneous process.

What is the criterion for spontaneity regarding Gibbs energy?

A spontaneous process corresponds to a negative Gibbs free energy change for a system.

Define DfG°298.

The change in Gibbs energy when 1 mol of a compound is formed at 1 bar and 298 K from its constituent elements in their most stable forms.

What is the equation for calculating DrG°T?

DrG°T ≈ DrH°298 – T DrS°298

What is chemical equilibrium?

A state where the Gibbs energy, G, is at a minimum, and there is no net production of either reactants or products.

What is the relationship between equilibrium constant K, and Gibbs energy?

∆rG° = –RT lnK

What is the van't Hoff equation?

ln K = -ΔrH°/(RT) + ΔrS°/R

State the Gibbs energy change equation.

DG = DH - TDS