Thermodynamics Flashcards

Questions and Answers

What is thermodynamics?

The set of laws that describe how energy and matter behave at a macroscopic level.

An enzyme would _ the reaction but wouldn't affect the __.

speed up, equilibrium

What does it mean that energy is a state function?

Energies of reactants to products are independent of the conversion pathway.

What is ΔH in a reaction?

ΔH is the heat generated or absorbed during a reaction. Signup and view all the answers

If ΔH is 0, heat is , and the reaction is .

absorbed, endothermic Signup and view all the answers

What is entropy?

A measure of disorder. Signup and view all the answers

What contributes to the entropy of a molecule?

Translational, rotational, and internal (vibrational) entropy. Signup and view all the answers

As temperature increases, how does entropy change?

Systems become more disordered. Signup and view all the answers

Match the following concepts regarding biological processes:

Entropy = Measure of disorder Enthalpy = Heat generated or absorbed Gibbs Free Energy = Combines enthalpy and entropy to determine reaction spontaneity Reaction Spontaneity = Depends on both enthalpy and entropy Signup and view all the answers

What is the relationship of enthalpy and entropy in spontaneous reactions?

Both enthalpy and entropy should be considered. Signup and view all the answers

What is Gibbs Free Energy change?

ΔG = ΔH - TΔS Signup and view all the answers

Is an exergonic reaction characterized by ΔG < 0?

True Signup and view all the answers

Is an endergonic reaction characterized by ΔG > 0?

True Signup and view all the answers

At equilibrium, ΔG = ______.

0 Signup and view all the answers

What is the significance of ΔH (-) and ΔS (+)?

It indicates the reaction is spontaneous at all temperatures. Signup and view all the answers

What occurs when ΔS > 0?

The reaction will more likely proceed as temperature increases. Signup and view all the answers

What is the relationship between Gibbs Free Energy and coupled reactions?

An unfavorable reaction can be coupled to a favorable one as long as the overall ΔG is < 0. Signup and view all the answers

What is ATP's role in coupled reactions?

ATP acts as the primary energy currency of living cells. Signup and view all the answers

The equation for the transport of uncharged molecules is ΔG = ______.

RT ln ([A]in/[A]out) Signup and view all the answers

What is the significance of electric potential difference in the transport of charged molecules?

It affects the Gibbs Free Energy equation for charged molecules. Signup and view all the answers

Study Notes

Thermodynamics Overview

Thermodynamics describes energy and matter behavior at the macroscopic level.
It predicts the macroscopic properties of chemical reactions, indicating direction and equilibrium but not reaction speed.

Enzymatic Influence

Enzymes speed up reactions but do not affect the equilibrium position.

Energy as a State Function

The energy change in a reaction is independent of the conversion pathway.
At equilibrium, the ratio of reactants to products remains consistent regardless of the mechanism.

Enthalpy

Enthalpy change (ΔH) represents the heat generated or absorbed during a reaction: ΔH = Hproducts - Hreactants.
A positive ΔH indicates absorbed heat, defining the reaction as endothermic.

Entropy

Entropy measures disorder; the universe tends towards increased disorder and is also a state function.
The entropy of a molecule includes contributions from translational, rotational, and internal motions.

Entropy and Molecular Interactions

Condensation of two molecules into one costs translational and rotational entropy.
Increased temperature typically results in higher system entropy.

Biological Processes

Biological systems balance entropy and enthalpy to drive reactions.

Entropic and Enthalpic Processes

Examples include DNA strand association (entropy decrease) and the hydrophobic effect (entropy increase).

Reaction Spontaneity

Determining reaction spontaneity requires both enthalpy and entropy considerations.
Gibbs Free Energy (G) combines both: ΔG = ΔH - TΔS.

Gibbs Free Energy

A negative ΔG indicates a spontaneous reaction; stability of products over substrates is key.
Factors influencing ΔG are enthalpy (ΔH) and entropy (ΔS).

Reaction Types

Exergonic: ΔG < 0 (spontaneous, can be endothermic or exothermic).
Endergonic: ΔG > 0 (not spontaneous, reverse reaction may be spontaneous).
Equilibrium: ΔG = 0 (no net reaction).

Temperature Effects on Reactions

Reactions with ΔH (-), ΔS (+) are spontaneous at all temperatures.
Reactions with ΔH (-), ΔS (-) can be spontaneous only below a specific temperature.
Reactions with ΔH (+), ΔS (+) are spontaneous above a certain temperature, while those with both ΔH (+) and ΔS (-) are unspontaneous.

Entropy Increase with Temperature

The TΔS term grows larger as temperature rises, influencing spontaneity.

Coupled Reactions

An unfavorable reaction can drive a favorable one if the overall ΔG remains less than zero, crucial in metabolic pathways.

ATP as Energy Currency

ATP hydrolysis is highly exergonic and can drive endergonic reactions, linking energy release and demand.

Transport Dynamics for Molecules

The transport of uncharged molecules follows the concentration gradient; ΔGo' is zero at equilibrium.
For charged molecules, the electric potential difference across membranes is significant in determining ΔG, incorporating both concentration and charge.

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Description

Explore the core concepts of thermodynamics through these informative flashcards. Understand the fundamental laws governing energy and matter at a macroscopic level, as well as the influence of enzymes on chemical reactions. Test your knowledge and reinforce your learning in this crucial science field.