A2 Salters Chemistry Agriculture and Industry

A summary of agriculture and industry

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  • Created by: R_Hall
  • Created on: 03-02-14 19:49

5.8 Bonding, Structure and Properties: a Summary

  • The properties of a solid substance are affected by-
  • 1. The type of particles it contains
  • 2. The way the particles are bonded together- the stronger the bonding, the higher the melting and boiling points, and the greater the substance's hardness
  • 3. The way particles are arranged relative to one another- one-dimensional structures (eg poly(ethene)) are generally flexible, and three-dimensional structures (eg. silica) are hard and gritty
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7.2 Equilibria and Concentrations

  • For a reaction at equilibrium, the concentration of products over the concentration of reactants will give a constant value. This is the equilibrium constant, Kc
  • The units for Kc vary from reaction to reaction, but van be worked out from the equilibrium expression
  • The composition of a system at equilibrium will adjust (if changed) to keep the value of Kc constant, providing the temperature stays constant
  • Changing concentration changes composition, but not Kc 
  • Changing pressure may affect composition, but doesn't change Kc
  • Changing temperature changes both composition and Kc value
  • Adding  catalyst doesn't affect either composition or Kc value
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11.3 The P Block: Nitrogen and Group 5

  • All group 5 atoms have a lone pair of electrons, which enable the atoms to form dative covalent bonds.
  • Nitrogen and phosphorous are constituent elements in living things and are essential for healthy plant growth
  • Nitrogen gas molecules are unreactive because of the strong triple bond holding atoms together. Before it can react, the bond must be broken
  • The bond enthalpy is very high and most reactions of molecular N2 have high activation enthalpies, requiring high temperatures and catalyst. For example, the Haber process requires temperatures of 200c
  • Ammonia (NH3) readily acts as a base and forms dative covalent bonds to H+ to give the ammonium ion. It also forms dative bonds to transition metal ions, so it acts as a good ligand in complexes
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