H432/01

• Explain why the boiling point of PH3 is lower than the boiling point of NH3.

  NH3 has hydrogen bonding OR PH3 does not have hydrogen bonding

  Hydrogen Bonding is stronger OR more energy to overcome hydrogen bonding
• Explain why the boiling point of PH3 is lower than the boiling point of AsH3.

  AsH3/As has more electrons (than PH3/P)

  In AsH3, stronger/more induced dipole-dipole interactions OR stronger/more London forces (than PH3) OR more energy required to overcome induced dipole-dipole interactions
• The reactivity of the Group 2 elements Mg-Ba increases down the group. Explain why.

  Atomic radius increases OR more shells OR more (electron) shielding

  Nuclear attraction decreases OR (outer) electron(s) experience less attraction

  Ionisation energy decreases OR less energy needed to remove electrons
• State what is meant by disproportionation

  Oxidation and Reduction of the same element
• Explain what is meant by the term enthalpy change of hydration

  (Enthalpy change when) 1 mole of gaseous ions react OR 1 mole of hydrated/aqueous ions are formed

  Gaseous ions dissolve in water OR gaseous ions dissolve in water OR gaseous ions form aqueous/hydrated ions
• Explain what is meant by the term average bond enthalpy

  Breaking of one mole of bonds

  In gaseous molecules
• The first ionisation energy of sodium is more endothermic than that of potassium. Explain why.

  For sodium:

  • Atomic Radius Smaller OR Fewer Shells
  • Nuclear Attraction Increases OR (outer) electron(s) experience more attraction
• The lattice enthalpy of sodium oxide is more exothermic than that of potassium oxide. Explain why.

  For sodium ions:

  • The ionic radius of sodium /Na+ is smaller
  • Na+ has stronger attraction to O2-
• Red blood cells contain haemoglobin. Explain using ligand substitutions:

  • How haemoglobin transports oxygen around the body
  • Why carbon monoxide is toxic

  O2 (coordinately or datively) bonds with Iron

  (When required) O2 is replaced by H2O OR CO2

  OR O2 is replaced by CO

  OR H2O OR CO2 is replaced by O2

  CO forms strong(er) bonds (than O2)
• Explain the significance of the expression: Kp > 1

  Equilibrium position (far) to the right
• Relative atomic mass is defined as 'the weighted mean mass compared with 1/12th mass of carbon-12'. Explain what is meant by the term weighted mean mass.

  (The mean/average mass) taking into account the relative abundancies of the isotopes
• A catalyst is used in the production of methanol. State two ways that the use of catalysts helps chemical companies to make their processes more sustainable and less harmful to the environment.

  • (Reaction can be carried out at) lower temperatures/lower energy demand
  • Less (fossil) fuels burnt/less CO2 emissions
• Explain what is meant by the enthalpy change of solution.

  (Enthalpy change for) 1 mole of a compound/substance/solid/solute dissolving
• The enthalpy changes of the solution of the magnesium halids show a trend from MgF2 to MgI2. Could you explain why it is difficult to predict whether the enthalpy change of solution becomes more exothermic or less exothermic down the group from MgF2 to MgI2?

  • Halide ion gets larger down the group (Ionic radius)
  • Lattice Enthalpy is less exothermic down group (Lattice Enthalpy)
  • Hydration enthalpy is less exothermic down group(Hydration Enthalpy)
  • Difficult to predict whether lattice enthalpy or hydration enthalpy has bigger effect (Enthalpy of Solution)
• A dynamic equilibrium exists in a closed system. State the other features of a dynamic equilibrium.

  • Rate of forwards reaction = rate of backwards reaction
  • Concentrations/pressure/temperature are constant/do not change