chem

• Electrochemistry


  Interconversion of electrical energy and chemical energy
• Electrochemical processes


  1. Redox reaction

  2. Energy released by spontaneous reaction - Electricity energy - Favorable RXN

  3. Electrical energy is used to cause nonspontaneous reaction to occur - Non-favorable RXN

  
• Balancing Redox Reactions


  1. Oxidation - reduction reactions (REDOX) are reactions where electrons are transferred from one species to another

  2. Reduction reactions - Electrons are gained by the species, Metal = Reducing agents

  3. Oxidation reactions - Electrons are given off by the species, Release electrons

  
• Electrochemical Cells


  Electrodes that dip into an electrolyte and in which a chemical reaction either uses or generates an electric current
• Salt Bridge


  • Allows the flow of ions but prevents the mixing of the different solutions that would allow direct reaction of the cell reactants
• Voltaic or Galvanic Cell

  Spontaneous Reaction - generates an electric current

  
• Equilibrium Constant and Free Energy


  Nonstandard Calculation = ΔG = nFEcell
• Faraday's constant = 96485
• Temperature = 25+273.15 = 298.15 K
• Steps to calculate ΔG and K

  1. Compute Ecell E=Ecath-Eanod

  2. Determine the number of electrons (n)

  3. Use ΔG = nFEcell to calculate ΔG

  4. Use the formula to calculate the equilibrium constant K

  
• Instruments of Optical Spectrometry


  Spectroscope, Colorimeter, Photometer, Spectrograph, Spectrometer, Spectrophotometer
• Types of Spectrometry


  1. Emission Spectroscopy - Stimulant = HEAT/ ENERGY

  2. Absorption Spectroscopy - Stimulus = LIGHT, Transmitted radiation = Hindi Naabsorb

  3. Photoluminescence Spectroscopy - Concern sa Light Absorbed & Emitted
• Light Sources for Atomic Absorption Spectroscopy


  • Tungsten filament lamp
  • Halogen lamp
  • Deuterium lamp
  • Hallow cathode
  • Globar
  • Nernst glower
• Prism


  • Parallel collimating, Under Defraction
• Grating


  • Uneven surface
• Concave Grating


  • No need for auxiliary collimating and focusing mirrors
• Holographic Grating


  • Laser technique for forming gratings on a plane or concave glass surface, exhibit superior groove shape and flatness
• Types of Radiation Filters

  • Interference Filter
  • Absorption Filter
  • Interferometer
• Double-Beam UV-Vis Instruments


  Well-suited for continuous reading of absorption spectra, Compensate for short-term fluctuations in radiant output of the source
• Absorption Law

  Also known as the Beer-Lambert Law or Beer's Law, How the amount of attenuation depends on the concentration of the absorbing molecules and the pathlength over which absorption occurs
• Limitations to Beer's Law
• Absorption spectrum


  The higher the R value, the higher the Linearity (Good), Linearly related
• To precipitate


  Control the pH 2 acidic
• Efficiency is proportional to the number of extractions
• Separation of Ions by Ion Exchange

  • Cation exchange, Anion exchange
• Retention time formula


  ts = tr + tm
• Band Broadening and Column Efficiency


  • Fronting and tailing makes quantitative analysis difficult, hard to measure area under the curve
• Variables Affecting Column Efficiency


  Plate heights can be decreased, and thus column efficiency increased, by decreasing the particle size of column packings, by lowering the viscosity of the mobile phase

  Increases in temperature reduce band broadening in most cases

  Column efficiency are usually superior with gas chromatographic columns
• Inversely related
• Formulas Sheet


  • Standard cell potential

  Nonstandard cell potential, Calculate Delta G and K

  Nernst equation

  Retention time formula