Topic 8 Thermodynamics

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Created by
Amelia Procter

Cards (22)

  • What is the enthalpy change of formation? [2]
    The enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions
  • What is bond dissociation enthalpy? [2]
    The enthalpy change when all the bonds of the same type in 1 mole of gaseous molecules are broken
  • What is the enthalpy change of atomisation of an element? [2]
    The enthalpy when 1 mole of gaseous atoms is formed from an element in its standard states
  • What is the meaning of first ionisation energy? [2]
    The enthalpy when 1 mole of gaseous +1 ions are formed from 1 mole of gaseous atoms
  • What if the meaning of first electron affinity? [2]
    The enthalpy change when 1 mole of gaseous -1 ions is formed from 1 mole of gaseous atoms
  • What is the meaning of second ionisation energy? [2]
    The enthalpy change when 1 mole of gaseous +2 ions are formed from 1 mole of gaseous +1 ions
  • What is the meaning of second electron affinity? [2]
    The enthalpy change when 1 mole of gaseous 2- ions are formed from 1 mole of gaseous -1 ions.
  • What is the meaning of enthalpy change of hydration? [2]
    The enthalpy change when 1 mole of aqueous ions are formed from 1 mole of gaseous ions
  • What is the meaning of enthalpy change of solution? [2]
    The enthalpy change when 1 mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution
  • What is the meaning of lattice enthalpy of formation? [2]
    The enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions
  • What is the meaning of lattice enthalpy of dissociation ? [2]
    The enthalpy change when 1 mole of solid ionic compound is completely dissociated into its gaseous ions under standard conditions
  • What does the theoretical lattice enthalpy mean for ionic compounds? [3]
    The purely ionic model of a lattice assumes that all the ions are spherical, and have their charge evenly distributed around them.
    But if you find the lattice enthalpy experimentally, the value that you get if often different.
    This is evidence that most ionic compounds have some covalent character.
  • Why are the ions in ionic lattices not spherical? [2]
    The positive and negative ions in a lattice aren’t usually exactly spherical. Positive ions polarise neighbouring negative ions to different extents and the more polarisation there is, the more covalent the bonding will be
  • How do molecules dissolve in water? [3]
    Water molecules can bond to the ions because oxygen is more electronegative than hydrogen, so it draws electrons towards itself, creating a dipole.
    The dipole means the positively charged hydrogen atoms can form bonds with negative ions and negatively charged oxygen atoms can form bonds with positive ions
  • What is the meaning of entropy? [2]
    Entropy is a measure if the number of ways that particles can be arranged and the number of ways that energy can be shared out between particles.
    The more disordered the particles are, the higher the entropy is.
  • Which value, high or low, indicates a high level of disorder for entropy? [1]
    A large/positive value
  • Why do solid particles have low levels of entropy? [1]
    Solid particles just wobble about at a fixed point- there’s hardly any disorder, they have the lowest entropy
  • Why do gas particles have a high level of entropy? [1]
    Gas particles whizz around wherever they like. They’ve got the most disordered arrangement of particles, so they have the highest entropy
  • How does the concentration of particles affect entropy? [2]
    The more particles you’ve got, the more ways they their energy can be arranged- so in a reaction like N2O4 -> 2NO2 entropy increases because the number of moles increases.
  • What is the meaning of free energy change? [2]
    Free energy change is a measure used to predict whether a reaction is feasible. If deltaG is negative or equal to 0, then the reaction might happen by itself. Free energy change takes into account the changes in enthalpy and entropy in the system.
  • What is the equation for Gibbs free energy change? [1]
    DeltaG+ DeltaH -TdeltaS
  • Name the equation that links T, DeltaH and DeltaS
    T= DeltaH/ DeltaS