Analysis  of  PerCARBONATE

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Sodium Percarbonate  has the formula:


It is used in cleaning compounds:
Sodium Carbonate solubilizes many greases:

Na2CO3 + 2 CH3(CH2)16COOR'  --->  CH3(CH2)16COONa + 2 R'OH + CO2 + H2O

Sodium Carbonate reacts with acids to release carbon dioxide

Na2CO3  + 2 HCl  --->   2 NaCl  + CO2  + H2O

Hydrogen Peroxide is a bleach.
"Unsaturated" Organic molecules frequently have color.
Hydrogen peroxide reacts with (oxidizes) these molecules to form colorless products.

RCH=CHR'   + H2O2   --->   RCHOHCHOHR'  or  RCOOH   or ??? etc

Hydrogen Peroxide also undergoes disproportionation, the simultaneous oxidation and reduction.
This produces water and oxygen gas.
This accounts for the effervesence seen when hydrogen peroxide solutions are heated or subject to catalysis (damaged skin releases peroxidase )
2 H2O2  --->  2 H2O + O2

The ANALYSIS (abbreviated!)

  1. Weigh into a reaction tube the UNKNOWN
  2. Set up the gas collection apparatus.
    Heat and collect the gas generated.
  3. Allow the reaction tube to cool so the gas collected from thermal expansion is removed from the collection flask.
  4. When the apparatus is cool, level the gas collection flask to bring the pressure to atmospheric pressure.
  5. Weigh the collection flask and residual water.  Measure the temperature of the residual water.
  6. Fill the collection flask to the top with water and reweigh.
  7. Convert the weight of water lost to volume and use the ideal gas law  PV=nRT to calculate the amount of oxygen generated.
  8. Convert the moles of oxygen generated to mass of H2O2 in the UNKNOWN.
  9. Make sure the reaction tube does not contain any condensed water. Heat to remove any condensed water if necessary.
  10.  Weigh the cool, dry reaction tube.  Convert the weight loss to per cent volatiles.
  11.  Carefully add the required amount of HCl to the reaction tube and residue.
  12.  Quantitatively transfer to an erlenmeyer flask and heat to boiling to remove dissolved carbon dioxide.
  13.  Titrate to the phenolphthalein end point with Sodium Hydroxide.
  14.  Calculate the % Sodium Carbonate in the UNKNOWN.

  RWK  10/9/2005