BCHM-3050 Study Guide - Summer 2018, Comprehensive Midterm Notes - Protein, Carboxylic Acid, Covalent Bond
12 Oct 2018
School
Department
Course
Professor
BCHM-3050
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Chapter 3: The Energetics of Life
Free Energy
Free Energy Change (ΔG) is a process that determines whether that process will require energy or
release energy.
A system is any part of the universe that we choose for study, and the system may be isolated, and thus
unable to exchange energy and matter with its surroundings. The system could also be closed, so it is
able to exchange energy but not matter, or the system can be open, so that both energy and matter can
pass between the system and surroundings.
1st Law of Thermodynamics
It states that in a closed system, the energy is conserved. Energy can be neither created nor destroyed.
oEnthalpy (ΔH) is when heat is released in the reaction, and is the reaction releases energy, it is
negative, and the energy within the system decreased as this energy was transferred as heat to
the surroundings.
oState Function depends only on the initial and final states of the system it describes, including
temperature, pressure, free energy, enthalpy, and entropy.
The change in enthalpy for any system is defined as the difference in the enthalpy
between the final and initial states of the system:
A reversible process (melting ice) is always at a near state of equilibrium. The defining features of the
equilibrium state for a system undergoing a reaction or process are that it is the lowest energy state for
the system, and the forward/reverse rates for the process are equal.
oLower energy states are favored over those of higher energy, and systems tend to adopt states of
lower energy.
An irreversible process (burning paper) happens when systems are set up far from an equilibrium state,
and then they drive toward a state of equilibrium.
Entropy (S) is the degree of randomness or disorder in the arrangement of a system.
Free Energy: The Second Law in Open Systems
The entropy of the universe is:
The criterion for a favorable process in a nonisolated system, at constant temperature and pressure, is
that ΔG is negative.
oProcesses accompanied by negative free energy changes are said to be exergonic, those for
which ΔG is positive is endergonic.
The Relationships between Free Energy, the Equilibrium State, and Non-Equilibrium Concentrations of
Reactants and Products
Law of Mass Action states that when the rates of the forward and reverse reactions are equal, the
system will be at equilibrium, and the ratio of products and reactants will be given by the mass action
expression:
find more resources at oneclass.com
find more resources at oneclass.com
Le Chatelier’s Principle states that a system at equilibrium will respond to any perturbation to the
equilibrium, by moving to reestablish the equilibrium state.
oIt predicted that the system would act to restore the equilibrium ratio of reactants and products
by increasing the concentrations of solutes C & D, and decreasing the concentrations of solutes
B & A.
** for any system not at equilibrium, there is a driving force toward the equilibrium state**
Standard Free Energy or (ΔG°) is related to the chemical standard state. The chemical standard state is
defined as
Pressure = 1 bar
T = 25°C (273.15) K
Solutes at concentrations of 1 M each
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Free energy change ( g) is a process that determines whether that process will require energy or release energy. A system is any part of the universe that we choose for study, and the system may be isolated, and thus unable to exchange energy and matter with its surroundings. The system could also be closed, so it is able to exchange energy but not matter, or the system can be open, so that both energy and matter can pass between the system and surroundings. It states that in a closed system, the energy is conserved. The change in enthalpy for any system is defined as the difference in the enthalpy between the final and initial states of the system: A reversible process (melting ice) is always at a near state of equilibrium. An irreversible process (burning paper) happens when systems are set up far from an equilibrium state, and then they drive toward a state of equilibrium.
