Topic 3 (quantitive chemistry)

• What is the calculation that links mass, volume and concentration?

  Mass = concentration x volume
• What is atom economy?

  the mass of the products you want as a percent of all the produced products mass

  atom economy = (mass of useful products / mass of all products) x100
• what is the method for a titration?

  measure 25cm3 of alkaline in burette

  fill a pippete with the acid and add to a conical flask

  place the flask on a white tile under burette

  add phenopthalein to flask

  slowly add the alkaline to flask while swirling

  when indicator goes clear, it has been neutralised and work out how much alkaline was used
• Why are you unlikely to get a 100% yeild?

  Raw materials may not be pure

  some products may be left in the apparatus

  reaction may not have finished

  may give unexpected products
• What is percentage yield?

  the amount of product you actually get as a percent of the ampunt you theoretically make
• how to calculate percentage yield?

  actual mass of product / max theoretical mass
• What calculation links moles, mass and molecular mass?

  Mass = moles x mr
• steps for reaction amount calculations?

  find the amount of moles in the known substance

  look at molar ratio

  number of moles x mr
• what is avagadros constant?

  6.022 x 10^23 molecules/mol
• what is the calculation that links volume, moles and 24?

  volume of a gas = moles x 24
• steps for a titration calculation?

  balance equation

  molar ratio

  how many moles of known

  how many moles of unknown

  concentration of unknown
• how to carry out a titration calculation?

  step 1 : calculate the amount of alkaline in moles

  conc in mol/dm3 = amount of solute in mol / volume in dm3

  step 2 : find the amount of acid in moles

  look at the molar ratio

  step 3 : calculate the concentration of acid in mol/dm3

  conc = amount of solute / volume in dm3

  Step 4 : calculate the concentration of acid in g / dm3