SPONTANEOUS REACTION

• Spontaneous Reaction


  Occurs when the reactants are mixed at specific conditions and the reaction occurred
• Nonspontaneous Reaction


  Occurs when the reactants are mixed at specific conditions and the reaction did not occur
• Spontaneous


  Developing or occurring without apparent external influence, force, cause, or treatment
• At temperature 100 °C and pressure 1 atm, water will spontaneously boil
• At temperature 100 °C and pressure 1 atm, salt will spontaneously dissolve in water

  
• Salt crystals will not spontaneously form from a salt solution
• Iron will spontaneously form rust when exposed to water and oxygen
• An apple will spontaneously rot if left in an open space for several days
• You cannot spontaneously transform a rotten apple into a fresh one
• Enthalpy (ΔH)


  A thermodynamics quantity used to describe heat changes taking place at constant pressure
• Most exothermic reactions are spontaneous, some endothermic reactions are also spontaneous
• Entropy (S)


  A measure of how dispersed the energy of a system is among the different ways that system can contain energy
• The entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process
• Second Law of Thermodynamics

  For a spontaneous process: ΔSuniv = ΔSsys + ΔSsur > 0, For an equilibrium process: ΔSuniv = ΔSsys + ΔSsur = 0
• Temperature


  The average translation kinetic energy of a system
• At higher temperatures, more energy gets distributed or dispersed, and more microstates are available
• Checking of Understanding


  1. Predict whether the following reactions are spontaneous or nonspontaneous:

  2. A spoon dipped in boiling water gets hot

  3. Water decomposes into hydrogen and oxygen gases with application of electricity

  4. Wood burns to ash after being set on fire

  5. Silverware tarnishes when exposed to air

  6. Table salt dissociates into sodium and chlorine ions in water

  7. Water molecules form from hydrogen and oxygen gases
• Decomposition of organic matter in a compost pile

  SPONTANEOUS
• Evaporation of water at room temperature

  SPONTANEOUS
• Synthesis of ammonia from nitrogen and hydrogen gas

  NON SPONTANEOUS
• Reaction between sodium and chlorine to form table salt

  SPONTANEOUS
• Growth of crystals in a supersaturated solution

  SPONTANEOUS
• Melting of ice cubes in a warm room

  SPONTANEOUS
• Rusting of iron

  SPONTANEOUS
• Combustion of gasoline in an engine

  SPONTANEOUS
• Dissolving of sugar in water

  SPONTANEOUS
• Formation of diamonds from carbon under high pressure and temperature

  SPONTANEOUS
• Freezing of water at sub-zero temperatures

  SPONTANEOUS
• Decomposition of hydrogen peroxide into water and oxygen gas

  NON SPONTANEOUS
• Photosynthesis in plants

  SPONTANEOUS
• Dissociation of sodium chloride into sodium and chloride ions in water

  NON SPONTANEOUS
• Digestion of food in the human body

  SPONTANEOUS
• Formation of rust-resistant coating on iron surfaces

  NON SPONTANEOUS
• Mixing of hot and cold water in a bathtub

  SPONTANEOUS
• Conversion of graphite to diamond under high pressure and temperature

  SPONTANEOUS
• Decomposition of ozone into oxygen molecules

  NON SPONTANEOUS
• Synthesis of protein molecules from amino acids in living organisms

  SPONTANEOUS