Module-01-Thermodynamics-and-Concentrations-Review

Internal Energy, U

Total energy (potential and kinetic) in a system.

Law of Conservation of Energy

The energy of an isolated system is constant; represented mathematically as ΔU = q + w.

First Law of Thermodynamics

An isolated system cannot exchange heat or work with its surroundings, thus ΔU (isolated system) = 0.

Enthalpy, H

Defined as H = U + PV, where U is internal energy, P is pressure, and V is volume.

ΔH

Change in enthalpy, calculated as ΔH = Hf - Hi, can be expressed as ΔH = ΔU + PΔV.

Standard State

The pure element or compound at a pressure of 1 bar and the temperature of interest.

Hess’s Law

States that if a process occurs in stages, the total enthalpy change is the sum of the enthalpy changes for the individual steps.

Entropy, S

A measure of disorder in a system; increases generally when pure liquids are formed, gases are produced, or temperature increases.

Standard Free Energy Change, ΔG°

The change in free energy for a reaction in which a substance in its standard state is formed from its elements.

Criteria for Spontaneous Change

If ΔGsys < 0, the process is spontaneous; if ΔGsys = 0, it is at equilibrium; if ΔGsys > 0, it is non-spontaneous.

Molarity, M

A concentration unit defined as moles of solute per liter of solution.

Parts per million, ppm

A concentration unit defined as mg/L or mg/kg.

Percent by mass

Mass of solute divided by the total mass of the solution, multiplied by 100.

Standard Enthalpy of Formation, ΔHf°

The enthalpy change that occurs in the formation of one mole of a substance in its standard state from the reference forms of elements.