Amount of Substance

• Mole (mol)

  Is a unit of measurement that is the amount of a pure substance containing the same number of chemical units (atoms, molecules, etc) as there are atoms in exactly 12 grams of carbon-12
• Number of particles equation

  Number of moles x Avogadro's constant
• Ar/Mr unit

  gmol^(-1)
• Number of moles equation

  Mass / Mr or Ar
• Concentration equation

  Concentration(g/dm*3)=mass(g)/volume(dm*3)

  Concentration (mol/dm*3)=number of moles/volume(dm*3)
• Volume of gas at room temperature equation

  V(dm^3)= number of moles(mol) X 24dm^3
• Limiting reactant

  Reaction will progress until one of the reactants run out (lower number of moles)
• Excess

  Reactant said to be left over (higher number of moles)
• Acid + Metal

  acid + metal -> salt + hydrogen
• Acid + metal carbonate

  salt + water + carbon dioxide
• Acid + metal oxide

  Acid + Metal Oxide -> Salt + Water
• Acid + metal hydroxide

  Acid + Metal Hydroxide -> Salt + Water
• Hydroxide ion

  OH-
• Nitrate ion

  NO3-
• Carbonate ion

  CO3 2-
• Ammonium ion

  NH4+
• Phosphate ion

  PO4 3-
• Concentration

  Amount of solute per volume of solvent
• Percentage error/% uncertainty

  (Uncertainty of equipment X number measurements) divide by value of measurement

  X100
• Volume of gas equation

  Volume of gas (dm3) = moles of gas X 24dm3
• When 2 or more gases react together we can equate ...

  Volumes instead of moles because the two are directly proportional
• Ideal Gas Equation

  PV=nRT

  where P = pressure

  V= volume

  n = number of moles

  R = the molar gas constant

  T = temperature
• units of pressure

  Pascals (Pa)
• units of volume

  m^3
• units of temperature

  Kelvin (K)
• dm3 to m3

  divide by 1000
• dm3 to cm3

  x1000
• cm3 to dm3

  divide by 1000
• cm3 to m3

  divide by 1,000,000
• MPa to Pa

  x1,000,000
• °C to K

  °C + 273
• Tonne to Kilograms

  x1000
• Making a volumetric/ standard solution (titration) -1

  -accurately weigh out a dry sample of the acid using a high precision balance

  -transfer to a beaker and reweigh weighing boat to determine mass transferred

  -dissolve acid in a small volume of distilled water, stirring with a glass rod

  -transfer to a volumetric flask and rinse all equipment
• Making a volumetric/ standard solution (titration) -2

  -transfer rinsings too

  -add deionised water up to calibration line using dropping pipette at end -ensure meniscus rests on calibration line and measure at eye level

  -stopper bottle and invert 10 times to homogenise the solution (to make sure concentration of solution is the same all the way through it)
• acid-base titration steps 1-6

  1. Rinse the burette with (the solution you know the concentration of) in order to remove any contamination

  2. overfill burette with (the solution you know the concentration of) and run through so jet space is filled

  3. use a volumetric pipette to transfer 25cm^3 of (the solution you don't know the concentration of) to a conical flask

  4. add 3 drops of phenolphthalein (suitable indicator)

  5. slowly add the (the solution you know the concentration of)

  6. swirl between additions (to homogenise the solution and ensure everything is reacting together)
• acid-base titration steps 7-10

  7. rinse the burette and sides of conical flask using a wash bottle of deionised water

  8. stop at first permanent colour change and record volume of (the solution you know the concentration of) added

  9. repeat titrations until concordant results are achieved

  10. use concordant data to calculate mean titre
• acid-base titration steps 11-13

  11. use n=c X v to calculate moles of (the solution you know the concentration of) added

  12. find mole ratio to calculate moles of (the solution you don't know the concentration of)

  13. use c= n/0.025 calculate the concentration of (the solution you don't know the concentration of)
• Why do we not add too many drops of indicator

  Because it could react with the reactant in the conical flask and affect the result of the titration
• Why do we use a conical flask (titration)

  To avoid and less chance of any splashing (when swirling)
• Why do we rinse the burette with the solution you are going to use and not water

  Because some water would be left behind afterwards and that would dilute the solution you were going to add, and this affects your results. Titre value would increase