L2 water

• bonding of water molecule

  2 covalent bonds between 1 oxygen and 2 hydrogen atoms
• sp3 hybrid orbitals are made of

  1 s orbital and 3 p orbtials
• hybridisation causes change in shape of the orbitals
• how many lone pairs does oxygen have when in H2O


  2
• define electronegativity

  tendency of an atom to attract electrons
• shape of water molecule

  tetrahedral
• water molecule angles

  104.5 degrees, due to lone pairs repelling more than bonding pairs
• does hybrid sp3 orbitals have higher or lower energy than the p orbital

  lower, because merge energy levels from s and p orbitals
• hydrogen bonding in water

  polar bonds draw on oxygen and hydrogen

  
• effects of hydrogen bonding on water

  higher boiling point (liquid at room temperature), higher cohesion (molecule drags another upwards), high heat of vapourisation (sweat cools), ice floats on water (has a lower density), higher surface tension (ordered arrangement of molecules), higher specific heat (resistance to change of temperature)
• water molecule polarity therefore:

  water is a good solvent for ionic compounds, oil drop effect (hydrophobic interactions)
• 1 mole of a compound always contains


  6.02*10^23 molecules
• Avogadro's number


  6.02*10^23 molecules
• 1 mole of a substance is equivalent to its molecular mass in grams
• 1 mole of water molecules

  18 grams
• 1 molar (1M) solution of a substance contains

  1 mole/litre of solution
• 1 litre= 1 dm^3
• hydronium ion

  H3O+
• hydroxide ion

  OH-
• water dissociation constant (Kw) is a universal constant
• water dissociation constant

  Kw

  
• to calculate pH=-log10[H+]
• pH of pure water

  7
• solution of pH 3 has [OH-] of 10^-11M, has [H+] of 10^-3, is a thousand times as acidic as a solution of pH 6
• water molecules bind to one another which enables water to have high surface temperature
• high surface temperature means some insects can walk on the surface of the water
• hydrogen bonding of water means that water is a liquid at room temperature meaning that lots of energy is required to break these bonds, therefore more heat
• specific heat capacity

  amount of heat that must be absorbed to raise temperature of 1g of that substance by 1 degree celcius (or Kelvin)
• water molecules make a crystal lattice as a result of being bonded to how many neighbouring water molecules

  4
• hydration shell to remove ionic crystal lattice atoms from one another means that the salt dissolves to give an aqueous solution of the crystal lattice
• water dissociation is a reversible reaction
• water dissociation reaches an equilibrium which means:


  rate of forwards reaction=rate of backwards reaction
• Kw in water stays constant at

  10^-14
• water is a polar molecule
• intramolecular forces in water

  covalent bonds
• intermolecular force in water

  hydrogen bonds
• molarity means

  the amount of solute per unit volume of solution