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Gibbs Free Energy quiz

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Terms in this set (15)

  • What does a negative ΔG value indicate about a chemical reaction?
    A negative ΔG means the reaction is spontaneous and will proceed without external energy input.
  • What is the relationship between ΔG and the equilibrium constant K?
    If ΔG is negative, K > 1 and products are favored; if ΔG is positive, K < 1 and reactants are favored; at equilibrium, ΔG = 0 and K = 1.
  • What are the standard conditions for thermodynamics?
    Standard conditions are 1 atmosphere pressure and 25°C (298 K) temperature.
  • What is the equation for ΔG under standard conditions?
    ΔG° = ΔH° - TΔS°.
  • What is the equation for ΔG under non-standard conditions?
    ΔG = ΔG° + RTlnQ, where R is the gas constant, T is temperature in Kelvin, and Q is the reaction quotient.
  • What states of matter are ignored when calculating the reaction quotient Q?
    Solids and liquids are ignored; only aqueous and gaseous species are considered.
  • What does it mean if ΔG under non-standard conditions is less than zero?
    The reaction is spontaneous under those conditions.
  • What does it mean if ΔG under non-standard conditions is greater than zero?
    The reaction is non-spontaneous under those conditions.
  • What does it mean if ΔG under non-standard conditions equals zero?
    The reaction is at equilibrium.
  • When are reactions with both ΔH and ΔS positive spontaneous?
    They are spontaneous at high temperatures.
  • When are reactions with both ΔH and ΔS negative spontaneous?
    They are spontaneous at low temperatures.
  • What is the spontaneity of a reaction with positive ΔH and negative ΔS?
    It is non-spontaneous at all temperatures.
  • What is the spontaneity of a reaction with negative ΔH and positive ΔS?
    It is spontaneous at all temperatures.
  • What is the value of the gas constant R used in the ΔG equation?
    R = 8.314 joules per mole per Kelvin.
  • How can you quickly determine reaction spontaneity using ΔH and ΔS values?
    Use a diagram with ΔS values on top and ΔH values on the side to remember: high (both positive), non-spontaneous (ΔH positive, ΔS negative), low (both negative), and spontaneous at all temperatures (ΔH negative, ΔS positive).