6 markers p1 chem

• The hydrogen used in a hydrogen-oxygen fuel cell can be produced from methanol

  $CH_3OH^{ }$$+$$\ H_2O$$\rightarrow\ CO_2\ +$$\ 3H_2$

  In this reaction the forward reaction is endothermic and heat energy is taken in from the surroundings.

  The conditions used for this reaction are

  •a nickel catalyst

  •a temperature of 220 °C

  Explain, their effects on the rate of attainment of equilibrium + equilibrium yield of hydrogen, why the reaction is carried out using a catalyst at 220 °C rather than without a catalyst at a lower temperature. part 1- effect of catalyst

  EFFECT OF CATALYST

  • increases rate of attainment of equilibrium so increases both forward + backwards reaction
  • lowers activation energy + provides alternate reaction pathway
  • no effect of equilibrium yield
• The hydrogen used in a hydrogen-oxygen fuel cell can be produced from methanol

  In this reaction the forward reaction is endothermic and heat energy is taken in from the surroundings.

  The conditions used for this reaction are

  •a nickel catalyst

  •a temperature of 220 °C

  Explain, their effects on the rate of attainment of equilibrium + equilibrium yield of hydrogen, why the reaction is carried out using a catalyst at 220 °C rather than without a catalyst at a lower temperature. part 2- temp effect

  EFFECT OF TEMP (HIGHER NOT LOWER)

  • faster rate of attainment of equilibrium
  • as particles have higher kinetic energy -> increased collision frequency so more successful collisions
  • equilibrium yield of hydrogen increases with higher temperatures
  • because thermal energy taken in forward reaction (endothermic)
  • increasing temperature shifts equilibrium further to right-hand side
• structure + bonding of substances A, B + C

  • substance A: MP- 1180, ability to conduct electricity solid- poor, molten- good
  • substance B: MP- 1538, solid- good, molten- good

  SUBSTANCE A:

  • giant ionic structure
  • high MP -> strong electrostatic forces between ions so a lot of energy required to overcome
  • solid ions strongly attracted in lattice so ions not move so poor conductor
  • molten ions = free to move so good conductor

  SUBSTANCE B:

  • metallic structure
  • high MP-> strong attraction between metal ions + delocalised electrons so a lot of energy required to overcome strong forces between particles in solid
  • solid: delocalised electrons free to move throughout metallic lattice
  • molten: delocalised electrons = free to move so good conductor
• structure + bonding of substance C: melting point - 115, ability to conduct electricity: solid- poor, molten- poor

  SUBSTANCE C:

  • covalent simple molecular
  • low MP-> weak intermolecular forces between molecules
  • little energy needed to separate molecules so low melting point
  • electrical conductivity in solid + when molten no delocalised electrons or ions to carry charge
  • so poor conductor