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Catégorie :Category: nCreator TI-Nspire
Auteur Author: trbtrbrtbrtbrb
Type : Classeur 3.0.1
Page(s) : 1
Taille Size: 4.92 Ko KB
Mis en ligne Uploaded: 17/04/2025 - 03:24:55
Mis à jour Updated: 17/04/2025 - 03:25:04
Uploadeur Uploader: trbtrbrtbrtbrb (Profil)
Téléchargements Downloads: 1
Visibilité Visibility: Archive publique
Shortlink : http://ti-pla.net/a4586876
Type : Classeur 3.0.1
Page(s) : 1
Taille Size: 4.92 Ko KB
Mis en ligne Uploaded: 17/04/2025 - 03:24:55
Mis à jour Updated: 17/04/2025 - 03:25:04
Uploadeur Uploader: trbtrbrtbrtbrb (Profil)
Téléchargements Downloads: 1
Visibilité Visibility: Archive publique
Shortlink : http://ti-pla.net/a4586876
Description
Fichier Nspire généré sur TI-Planet.org.
Compatible OS 3.0 et ultérieurs.
<<
<! Thermodynamics Entropy Entropy is the level of disorder in a system, or how well dispersed the particles are. Entropy levels from lowest to highest: Solids (lowest entropy) Liquids Aqueous Solutions Gases (highest entropy) Factors that increase entropy: Raising the temperature (molecules move faster) Increasing the volume for a gas (molecules have more space) Chemical reaction from all solid to a mix of solid and gas More molecules of gas in a chemical reaction Calculating Entropy To calculate the entropy of a reaction: $S_{reaction} = £S_{products} - £S_{reactants}$ Identical to calculating change in enthalpy Gibbs Free Energy Thermodynamically favored: A process that tends to occur. Gibbs Free Energy (G): A measure of the thermodynamic favorability of a chemical process. G < 0: Thermodynamically favored G > 0: Not favored Standard Conditions Standard conditions are usually indicated by a degree sign (°). Standard conditions include: 25 degrees Celsius 1 atmosphere pressure 1 mole per liter for solutions Calculating Gibbs Free Energy Two ways to calculate G: $G = £G_{products} - £G_{reactants}$ $G = H - TS$ (T is Kelvin temperature) Careful with units: Entropy is usually in Joules, while enthalpy and Gibbs Free Energy are usually in kilojoules. Thermodynamic Favorability The universe favors: Exothermic reactions (negative H) Reactions where entropy is increasing (positive S) Thermodynamic Favorability Conditions: H S Favorability at: Negative Positive All temperatures Positive Negative No temperature Positive Positive High temperatures Negative Negative Low temperatures Kinetic Control Kinetic Control : When a reaction is thermodynamically favored but has an immeasurably slow rate, often due to a very high activation energy. The reaction is not at equilibrium, but it is very slow or may not occur at all. Gibbs Free Energy and the Equilibrium Constant Relationship between Gibbs Free Energy and the equilibrium constant (K): $G = -RTlnK$ R = 8.314 Joules per mole per Kelvin Implications: If G is negative, K is a very large number (thermodynamically favored, lots of product). If G is positive, K is a very small number (not favored, almost no products form). Dissolution Every ionic compound can potentially dissolve and dissociate in water. Consider potassium chloride (KCl) dissociating in water: $KCl(s) Ì K^+(aq) + Cl^-(aq)$ If G is negative, the process is thermodynamically favored (e.g., KCl IS soluble in water). Driving forces: enthalpy and entropy Examine H and S to predict if a compound will dissolve and under what conditions. A positive change in enthalpy is NOT favored. A positive change in entropy IS favored. Reactions Some thermodynamically unfavorable reactions can still happen by: Adding external energy (electricity, light) Coupling the unfavorable reaction with a more favorable one Example: Obtaining copper from copper(II) sulfide: $CuS(s) + O_2(g) Cu(s) + SO_2(g)$ The reaction of copper(II) sulfide with oxygen has a negative delta G. = Electrochemistry Galvanic Cells Galvanic Cell: A battery that harnesses the electron flow of a redox reaction to power a load. Diagram: A visual representation of the galvanic cell. Anode: The side where oxidation takes place. Cathode: The side where reduction takes place. "RED CAT and AN OX" Electrons flow from the anode to the cathode. (A/C) Metallic electrodes: Cathode increases in mass ("The CAT gets FAT"). Salt bridge: Equalizes the charge as ions react at the electrodes. Uses ions that wont react (e.g., sodium and nitrate ions). Cations flow toward the cathode, and anions flow toward the anode. Cell Potential Cell Potential : The voltage or potential difference of a galvanic cell. $E_{cell} = E_{cathode} - E_{anode}$ Half-reactions are written as reduction potentials. Cell Potential and Thermodynamic Favorability $G = -nFE_{cell}$ n = number of electrons transferred F = Faradays constant (96,485 coulombs per mole of electrons) Implications: Positive voltage: thermodynamically favored Negative voltage: unfavored, needs an external power source Non-Standard Conditions Nernst Equation : Used for non-standard conditions (temperature and concentration). If we increase the concentration of the products, or decrease the reactants, that increases the reaction quotient Q, and that lowers the voltage. Decreasing the concentration of the products or increasing the reactants, will decrease the value of Q, and that raises the voltage. A galvanic cell at equilibrium is a dead battery and has a voltage of zero! Electrolytic Cells Electrolytic Cells : Non-favored processes driven by an external power source, often used for plating out metals. $Current (amps) = rac{Total Quantity}{}$ Electrolysis and Stoichiometry >ê Electrolysis involves using electrical energy to drive non-spontaneous chemical reactions. The amount of substance produced or consumed at an electrode during electrolysis is related to the quantity of charge passed through the
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Compatible OS 3.0 et ultérieurs.
<<
<! Thermodynamics Entropy Entropy is the level of disorder in a system, or how well dispersed the particles are. Entropy levels from lowest to highest: Solids (lowest entropy) Liquids Aqueous Solutions Gases (highest entropy) Factors that increase entropy: Raising the temperature (molecules move faster) Increasing the volume for a gas (molecules have more space) Chemical reaction from all solid to a mix of solid and gas More molecules of gas in a chemical reaction Calculating Entropy To calculate the entropy of a reaction: $S_{reaction} = £S_{products} - £S_{reactants}$ Identical to calculating change in enthalpy Gibbs Free Energy Thermodynamically favored: A process that tends to occur. Gibbs Free Energy (G): A measure of the thermodynamic favorability of a chemical process. G < 0: Thermodynamically favored G > 0: Not favored Standard Conditions Standard conditions are usually indicated by a degree sign (°). Standard conditions include: 25 degrees Celsius 1 atmosphere pressure 1 mole per liter for solutions Calculating Gibbs Free Energy Two ways to calculate G: $G = £G_{products} - £G_{reactants}$ $G = H - TS$ (T is Kelvin temperature) Careful with units: Entropy is usually in Joules, while enthalpy and Gibbs Free Energy are usually in kilojoules. Thermodynamic Favorability The universe favors: Exothermic reactions (negative H) Reactions where entropy is increasing (positive S) Thermodynamic Favorability Conditions: H S Favorability at: Negative Positive All temperatures Positive Negative No temperature Positive Positive High temperatures Negative Negative Low temperatures Kinetic Control Kinetic Control : When a reaction is thermodynamically favored but has an immeasurably slow rate, often due to a very high activation energy. The reaction is not at equilibrium, but it is very slow or may not occur at all. Gibbs Free Energy and the Equilibrium Constant Relationship between Gibbs Free Energy and the equilibrium constant (K): $G = -RTlnK$ R = 8.314 Joules per mole per Kelvin Implications: If G is negative, K is a very large number (thermodynamically favored, lots of product). If G is positive, K is a very small number (not favored, almost no products form). Dissolution Every ionic compound can potentially dissolve and dissociate in water. Consider potassium chloride (KCl) dissociating in water: $KCl(s) Ì K^+(aq) + Cl^-(aq)$ If G is negative, the process is thermodynamically favored (e.g., KCl IS soluble in water). Driving forces: enthalpy and entropy Examine H and S to predict if a compound will dissolve and under what conditions. A positive change in enthalpy is NOT favored. A positive change in entropy IS favored. Reactions Some thermodynamically unfavorable reactions can still happen by: Adding external energy (electricity, light) Coupling the unfavorable reaction with a more favorable one Example: Obtaining copper from copper(II) sulfide: $CuS(s) + O_2(g) Cu(s) + SO_2(g)$ The reaction of copper(II) sulfide with oxygen has a negative delta G. = Electrochemistry Galvanic Cells Galvanic Cell: A battery that harnesses the electron flow of a redox reaction to power a load. Diagram: A visual representation of the galvanic cell. Anode: The side where oxidation takes place. Cathode: The side where reduction takes place. "RED CAT and AN OX" Electrons flow from the anode to the cathode. (A/C) Metallic electrodes: Cathode increases in mass ("The CAT gets FAT"). Salt bridge: Equalizes the charge as ions react at the electrodes. Uses ions that wont react (e.g., sodium and nitrate ions). Cations flow toward the cathode, and anions flow toward the anode. Cell Potential Cell Potential : The voltage or potential difference of a galvanic cell. $E_{cell} = E_{cathode} - E_{anode}$ Half-reactions are written as reduction potentials. Cell Potential and Thermodynamic Favorability $G = -nFE_{cell}$ n = number of electrons transferred F = Faradays constant (96,485 coulombs per mole of electrons) Implications: Positive voltage: thermodynamically favored Negative voltage: unfavored, needs an external power source Non-Standard Conditions Nernst Equation : Used for non-standard conditions (temperature and concentration). If we increase the concentration of the products, or decrease the reactants, that increases the reaction quotient Q, and that lowers the voltage. Decreasing the concentration of the products or increasing the reactants, will decrease the value of Q, and that raises the voltage. A galvanic cell at equilibrium is a dead battery and has a voltage of zero! Electrolytic Cells Electrolytic Cells : Non-favored processes driven by an external power source, often used for plating out metals. $Current (amps) = rac{Total Quantity}{}$ Electrolysis and Stoichiometry >ê Electrolysis involves using electrical energy to drive non-spontaneous chemical reactions. The amount of substance produced or consumed at an electrode during electrolysis is related to the quantity of charge passed through the
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