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Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
Ppt 9 thermochemistry
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Ppt 9 thermochemistry

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  • Q: In a test tube, why do chemical reactions occur? - likely have heard of two major forms of energy Q: Which is it for chemical reactions? Q: Where is the energy stored for chemical reactions?
  • Q: What other “law” is that similar to? - law of constant mass
  • Q: How much energy does a bond hold? Q: What would be a good way to test that out? - describe the experiment that was done 1) Difficult to look at one molecule  easier for a mole of molecules 2) Zap them with energy 3) Determine how much energy was used
  • Q: Given single and double bonds, which do you suppose requires more energy to break?
  • - we have reactions that release energy and form energy (exothermic and endothermic) Q: How does that work?
  • - energy of chemical reactions can be visualized in a graphical representation 1) x-axis represents progress of the reaction 2) y-axis represents energy of the components -need to indicate energy of the reactants and products Q: Given this difference between reactants and products, what type of reaction is depicted here?
  • Q: What is the purpose of metabolism? - to utilise the energy it produces
  • Q: But we’re continually losing heat... is the universe going to break down and collapse to heat?
  • - energy of chemical reactions can be visualized in a graphical representation 1) x-axis represents progress of the reaction 2) y-axis represents energy of the components -need to indicate energy of the reactants and products Q: Given this difference between reactants and products, what type of reaction is depicted here?
  • Q: How much work energy is available in a reaction in equilibrium? - 0
  • Take a look at the triphosphate. Q: What is the overwhelming charge? - negative Q: Why is this unstable? - likes repel
  • Q: What type of reaction is this? - hydrolysis - catabolism
  • Q: What happens to the energy? - it needs to be focused
  • Q: What reaction do you know of that would be classified as redox? - NaCl
  • - redox is the condensation of the two terms reduction and oxidation - clearly, these reactions are coupled (can’t have one without the other)
  • Transcript

    • 1. Themodynamics
    • 2. Energy <ul><li>the ability to do work </li></ul><ul><li>Kinetic – energy due to movement </li></ul><ul><li>Potential – stored energy </li></ul>Chemical potential energy is stored up in the bonds of a molecule.
    • 3. First Law of Thermodynamics <ul><li>The total amount of energy in the universe is constant. </li></ul><ul><li>Energy cannot be created or destroyed. </li></ul>
    • 4. H + H + H + H + H + - - - - -
    • 5. Bond Energy <ul><li>Chemical energy is stored in the bonds of the molecules. </li></ul><ul><li>The energy stored in the reaction is called free energy because it is available to do work. </li></ul><ul><li>The symbol for free energy is the letter G (in honour of Josiah Willard Gibbs who developed the concept of free energy). </li></ul>
    • 6. Bond Energies <ul><li>Measured in kJ / mol (kilojoules per mole) </li></ul><ul><li>Double bonds require more energy to break than single bonds </li></ul><ul><li>The greater the bond energy, the more stable the bond. </li></ul>Bond Type Average Bond Energy (kJ/mol) H-H 436 C-H 411 O-H 459 N-H 391 C-C 346 C-O 359 C=O 799 O=O 494
    • 7. Bond Energies <ul><li>exothermic reactions – energy released </li></ul><ul><li>endothermic reactions – energy absorbed </li></ul><ul><li>energy is required to break bonds </li></ul><ul><li>energy is released to form bonds </li></ul>
    • 8. Potential Energy Diagram EXOTHERMIC REACTION Why is that little hill labeled, Ac? Ac = activation energy. The energy required to release the free energy.
    • 9. <ul><li>Activation energy is the amount of energy necessary to push the reactants over an energy barrier. </li></ul><ul><ul><li>The difference between free energy of the products and the free energy of the reactants is the delta G. </li></ul></ul>Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.12
    • 10. Video Clips <ul><li>Hydrogen Explosion </li></ul><ul><li>http://www.youtube.com/watch?v=NYC23ANpEds </li></ul><ul><li>Activation Energy Example </li></ul><ul><li>http://www.youtube.com/watch?v=VbIaK6PLrRM&NR=1 </li></ul><ul><li>Activation Energy Song </li></ul><ul><li>http://www.youtube.com/watch?v=XgiCn1IpvzM </li></ul>
    • 11. Exothermic Reaction
    • 12. Potential Energy Diagram Absorbs energy
    • 13. Second Law of Thermodynamics <ul><li>The universe is becoming more disordered. </li></ul><ul><li>entropy – a measure of randomness / disorder </li></ul><ul><ul><li>greater entropy = greater disorder </li></ul></ul><ul><li>metabolise glucose into CO 2 and H 2 O </li></ul><ul><li>C 6 H 12 O 6 + O 2  CO 2 + H 2 O + energy </li></ul>
    • 14. <ul><li>Spontaneous processes are those that can occur without outside help. </li></ul><ul><ul><li>The processes can be harnessed to perform work. </li></ul></ul><ul><li>Nonspontaneous processes are those that can only occur if energy is added to a system. </li></ul>
    • 15. Gibbs Free Energy <ul><li>Energy that can do work </li></ul><ul><ul><li>Heat is “useless” as it dissipates </li></ul></ul><ul><li> G = G final – G initial </li></ul><ul><li>For a system to be spontaneous, the system must either give up energy (decrease in H-enthalpy), give up order (increase in S-entropy), or both. </li></ul><ul><ul><li>Delta G must be negative. </li></ul></ul><ul><ul><li>The greater the decrease in free energy, the greater the maximum amount of work that a spontaneous process can perform. </li></ul></ul><ul><li> G is negative for spontaneous reactions (the rxn moves forward) </li></ul><ul><li> G is positive for reactions that require energy (rxn moves in the reverse direction) </li></ul>
    • 16. Gibbs Free Energy <ul><li>Exergonic reaction – spontaneous, -  G </li></ul><ul><li>Endergonic reaction – not spontaneous, +  G </li></ul><ul><li>C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O  G = -2870 kJ/mol </li></ul><ul><li>6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2  G = +2870 kJ/mol </li></ul>Δ G = G final – G initial
    • 17.  G 20 240 140 20 140 240 Δ G = G final – G initial Please determine the activation energy and Δ G
    • 18. Equilibrium Equilibrium reactions convert back and forth with minimal energy. For equilibrium reactions:  G = 0
    • 19.  
    • 20.  
    • 21. Adenosine Triphosphate <ul><li>ATP is the primary free energy source for cells </li></ul><ul><li>ATP ADP + P i </li></ul><ul><li>+ energy </li></ul><ul><li> H 2 O </li></ul><ul><li> G = -31 kJ/mol </li></ul><ul><li>in the cell,  G is closer to -54 kJ/mol </li></ul>ATPase
    • 22. Phosphorylation <ul><li>ATP hydrolysis does not occur on its own. </li></ul><ul><li>Often, the energy is focused through phosphorylation of enzymes. </li></ul><ul><li>ATP is replenished through cellular respiration. </li></ul>Reminder Hydrolysis – reaction reacts with water to break the molecule.
    • 23.  
    • 24. Redox Reactions <ul><li>reactions involving electron transfer </li></ul>
    • 25. Redox Reactions <ul><li>Reduction – chemical reaction where an atom gains electrons </li></ul><ul><li>Oxidation – chemical reaction where an atom loses electrons </li></ul><ul><li>L oss G ain </li></ul><ul><li>E lectron E lectron </li></ul><ul><li>O xidation R eduction </li></ul>LEO the lion says GER
    • 26. Redox Reactions <ul><li>Reducing Agent – substance that LOSES electrons; it causes the other substance to be reduced </li></ul><ul><li>Oxidizing Agent – substances that GAIN electrons; it causes the other substance to be oxidized </li></ul>
    • 27. Redox in the Cell <ul><li>Many metabolic processes consist of chains of redox reactions. </li></ul>A - A B - B C - C D D -

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