Quantitative chemistry

• law of conservation of mass; no atoms are lost or made during a chemical reaction
• Explain change of mass (more detailed questions with mass use it)

  the mass appears to have decreased because there products _ escaped through the air. the total mass of the solid + gas is _ (most of the time it is the product) yet the mass of solids (reactants) is _
• Avogadro constant - 6.022 x 10^23
• Mole triangle

  A) mass

  B) moles

  C) Mr

  
• reaction in closed system

  • no substance can enter or leave
  • only energy is transferred in or out
• Reactions in non enclosed system

  • if gas escapes the total mass will look as though it has decreased. yet if gas enters it looks as though the mass has increased
• non enclosed reaction examples

  • copper carbonate decomposes on heating to make solid copper oxide, which stays in the boiling tube, and carbon dioxide gas, which escapes
  • magnesium reacts with oxygen, gained from the air, to produce magnesium oxide
• Reacting masses

  1.)Mr

  2.)moles - mass over mr

  3.) ratio

  4.) Mass - moles x mr
• The greater the amount of moles in the limiting reactant, the greater the amount of moles in the products
• Concentration triangle

  A) moles

  B) conc

  C) volume

  
• If we increase the mass of the solute and keep the volume the same then we increase the conc

  yet if we increase the volume of solution and keep the mass of the solute the same then we decrease the conc
• atom economy - mr of desired product over mr of total
• volume at room temp = no. of moles x 24
• Concentration

  1.) cnv underneath given equations

  2.) moles - conc x volume

  3.) ratio

  4.) conc or vol - moles over conc or vol

  4a.) if converting to g/mol then times the dm^3/mol by the mr
• 1. Use the pipette and add 25 cm3 of alkali to conical flask.
  2. Add a few drops of indicator and put the conical flask on a white tile.
  3. Fill the burette with acid and note the starting volume.
  4. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
  5. Stop adding the acid when when the indicator first permanently changes colour. Note the final volume reading.
  6. Repeat steps until you get concordant titres