Transcribed By Angela Vivien Dela Cruz Lorraine Claire Lanuza Course Professor s Mr Luisito Salting Jr Topics Entropy and Free Energy ENTROPY FREE ENERGY AND EQUILIBRIUM Spontaneous Process forward A spontaneous reaction is a reaction that occur under a given set of condition at a certain temperature pressure and concentration This process does not need external energy to move Process will naturally proceed for example Waterfall running downhill not upward Lump of sugar dissolves in a cup of coffee A gas expands in an evacuated bulb Water freezing below 0 C and ice melting but will not spontaneously reappear in its original form above 0 C Remember Heat flows from a hotter object to a colder object left to right chemical process It adheres to the law of diffusion which states that gas molecules begin in a highly concentrated volume and diffuse to an evenly distributed concentration in order to attain equilibrium Enthalpy Does a decrease in energy mean a reaction process is spontaneous In Enthalpy Negative energy after the reaction is more favorable because it is more stable exothermic reaction However this does NOT apply in all spontaneous processes Ex H O s H O l is spontaneous when H enthalpy Hence enthalpy is NOT ABSOLUTE in determining Higher disorder in the system will have higher entropy attaining higher spontaneity Ex Breaking of glass from one entity to shattered pieces For any substance the solid state is more ordered than the liquid state and the liquid state is more ordered than the gas state Large space between molecules will have more freedom of movement and will have higher entropy Remember S 0 positive entropy will always be considered because of high disorder Solids limited movement Liquids there are available spaces Microstates Available arrangement for molecules to occupy Will only vibrate microstate Can move in the X Y or Z plane vibrate and microstate Free movement microstate Gases larger spaces available temperatures esp At rotate high microstate entropy disorder randomness liq gas temperature Lower values will have more solid properties microstate entropy disorder spontaneity Entropy S Entropy is a measure of the randomness or disorder of is a quantitative matter which can predict a system It spontaneity better than enthalpy Disorder is a natural occurrence DELA CRUZ LANUZA BATCH 2024 S Sf Si Computing Microstates W number of microstates S k ln W k Boltzmann constant Page 1 of 6 Transcribed By Angela Vivien Dela Cruz Lorraine Claire Lanuza Course Professor s Mr Luisito Salting Jr Topics Entropy and Free Energy Wf Wi then S 0 Wf Wi then S 0 S k ln Wf Wi S 0 Solid to liquid Liquid to vapor Entropy is a State Function State function properties that are determined by the state of the system regardless of how that condition was achieved Properties independent to the path Initial and final states will only matter Ex energy enthalpy pressure volume Using Standard Entropy Values Standard Ambient Temperature and Pressure SATP temperature entropy 298 15 K 25 First and Second Laws of Thermodynamics First Law of Thermodynamics Second Law of Thermodynamics Energy can be converted from one form to another but energy cannot be created or destroyed Law of conservation of energy The entropy of increases Suniv Ssys Ssurr 0 the universe in a spontaneous process and remains unchanged in an equilibrium process Spontaneous Positive system surroundings system will give heat to surroundings ex We can feel the heat of boiling water when we are near it Suniv Ssys Ssurr 0 Equilibrium Forward reaction reverse reaction Entropy Changes in the System Ssys DELA CRUZ LANUZA BATCH 2024 The Standard Entropy of Reaction S rxn is the entropy change for a reaction carried out at 1 atm and 25 C aA bB cC dD S rxn cS C dS D aS A bS B S rxn nS products mS reactants Note stoichiometric a x standard entropy value A When gases are produced or consumed If a reaction produces more gas molecules than it consumes S 0 If the total number of gas molecules diminishes S 0 If there is no net change in the total number of gas molecules then S may be positive or negative BUT S will be a small number Entropy Changes in the Surroundings Ssurr If exothermic Ssurr 0 If endothermic Ssurr 0 Third Law of Thermodynamics The entropy of a perfect crystalline substance is zero at the absolute zero of temperature At 0 kelvin absolute zero all molecular movement will stop creating a perfect crystalline structure S k ln W W 1 S 0 absolute entropy no possible motion Bose Einstein Condensate an application of the third law of thermodynamics Still theoretical but now accepted Standard Free Energy The standard free energy of reaction G rxn is the free energy change for a reaction when it occurs under standard state conditions G rxn c G f c d G f D a G f A b G f B Page 2 of 6 Transcribed By Angela Vivien Dela Cruz Lorraine Claire Lanuza Course Professor s Mr Luisito Salting Jr Topics Entropy and Free Energy G rxn n G f products m G f reactants Standard free energy of formation G f is the free energy change that occurs when 1 mole of the compound is formed from its elements in their standard states G f of any element in its stable form is zero Ex Hydrogen upon formation it will produce a certain amount of energy and will produce standard free energy of formation H2 is the most stable form of hydrogen hence G f 0 Gibbs Free Energy G Spontaneous Process Suniv Ssys Ssurr 0 Equilibrium Process Suniv Ssys Ssurr 0 For a constant temperature and constant pressure process the formula is G Hsys T Ssys G 0 The reaction is spontaneous in the forward direction G 0 G 0 The reaction is nonspontaneous as written The reaction is spontaneous in the reverse direction The reaction is at equilibrium Pertains to the absence of spontaneity It is a mix of enthalpy and entropy which can be the best determiner of spontaneity G is favorable when negative Conventions for Standard States State of Matter gas Liquid Solid Standard State 1 atm pressure Pure liquid Pure solid Elements G f 0 most stable allotropic form at 25 and 1 atm Solution 1 molar concentration The Relationship of G H and S G H T S H S G Reaction proceeds spontaneously at high temperature At low temperatures the reaction is spontaneous in the reverse direction H is not favorable G is always positive Reaction is spontaneous in the reverse direction at all temperatures Both H and S are not nonspontaneous in all conditions favorable is always negative Reaction proceeds G spontaneously at all