Chemistry for life.

Shapes of molecules:

6 groups=octahedral-90

5 groups=trigonal bipyramidal-90/120

4 groups=tetrahedral-109

3 pairs and 1 lone=pyramidal-109

2 pairs and 2 lone=bent-109

3 groups=planar triangular-120

2 groups=linear 180

REMEMBER! Electrons repel eachother as far as possible=shape of molecules.

Enthalpy change of combustion (kJmol-1) =Energy transferred (kJ)/moles of fuel used.

Bond enthalpies;

    Shorter bonds have higher bond enthalpies than longer ones.

                          Shorter bonds are stronger than longer ones.

                          Double bonds are shorter than single bonds.

Standard enthalpy change of combustion-the enthalpy change when 1 mole of a substance burns completely in oxygen under standard conditions=298K

Aliphatic=No ring structures: Alkanes, Alkenes, Cycloalkanes.

Aromatic=Contain one or more benzene rings

Saturated=No double bonds.

Unsaturated=Contains one or more double bonds.

Group 2 oxides/hydroxides=bases that allow them to react with carbon dioxide/acids to form group 2 carbonates.

Solubility of group 2 carbonates decreases down the group.

Reactivity of group 2 increases down the group.

Thermal stability of group 2 carbonates increases down the group. 

Cracking-breaking up long chain molecules, into shorter, branched and unsaturated molecules.

Zeolites-small sieve like holes, only allow straight chain molecules through.

Wedges-bonds in front of the plane of paper

Dotted lines-bonds behind the plane of paper.

Same element same protons different numbers of neutrons.