chem. reactions U.2 L.2

  • thermodynamics is the science that studies the transfer of thermal energy, all activities involve changes in energy

  • laws of thermodynamics include

    1. conservation of mass energy - energy can neither be created nor destroyed but it can be transformed from one type into another and transferred from one object to another

    2. law of entropy - during any process, the universe tends towards disorder

  • the first law of thermodynamics

    • also referred to as the law of the conservation of energy

    • refers to maintaining the same amount of energy throughout a process

    • released energy could be transformed into mechanical energy (contracting muscle) and the rest into heat or other forms of energy

    • all the energy is accounted for

    • essential to demonstrate the form of energy change

  • endergonic vs. excergonic reactions

  • bond energy

    • measure of covalent bond stability

    • more stable = more energy

    • energy released when bond is formed energy is absorbed when bonds are broken

  • energy is required to break or form a chemical bond

  • whenever a chemical bond forms between two atoms, energy is released

  • different KJ of energy required to break 1 mole of bonds between 2 types of atoms

  • energy and condensations (anabolic)

    • bonds broken

      1. o-c 🠮 358 kJ/mol

      2. n-h 🠮 391kJ/mol

        = 749kJ/mol

    • bonds formed

      1. c-n 🠮 305 kJ/mol

        749 - 305 = net input of 444 kJ/mol

        • not spontaneous reactions

  • energy and hydrolysis (catabolic)

    • bonds broken

      1. o-c 🠮 358kJ/mol

        = 358kJ/mol

    • bonds formed

      1. o-h 🠮 463kJ/mol

      2. o-c 358kJ/mol

        358 - 821 = -463 kJ/mol

        net output of 463kJ/mol

    • spontaneous reactions

  • oxidation reduction (redux) reactions releases energy during the transfer from one reactant to another

  • oxidation : loss of electrons from one substance

  • reduction : addition of electrons to another substance

  • Loss of Electrons is Oxidation says Gain of Electrons is Reduction

  • coupled redox (reduction and oxidation at the same time) reaction : relative strengths of oxidizing agents B<C<D (D is the strongest oxidizing agent)

  • an acid and a base combine to create a salt and water

    HCl + NaOH → H 2 O + NaCl

  • buffers minimize change in the [H+] and [OH-] in a solution, they donate of accept H+ ions