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Washing soda is a hydrated compound whose formula can be written NA2CO3 xH2O, where x is the number of moles of H2O per mole of Na2CO3. When a 2.123g sample of washing soda was heated at 130*C, all of the water of hydration was lost, leaving the 0.786g of anhydrous sodium carbonate. Calculate the value of x

Respuesta :

kenmyna

The value of X  is  10  hence  the   of hydrated washing  soda  is  Na2CO3.10H2O


 calculation

Step 1: calculate the mass of water

 =  mass  of   hydrated washing   soda -  mass   of anhydrous sodium carbonate ( anhydrous   washing  soda)

 = 2.123 g - 0.786 g =1.337  grams

Step 2: calculate the moles of Na2CO3  and that of H2O  using moles=mass/molar  mass formula


  • molar mass of Na2CO3=  (2x23) + 12 + ( 16 x3)  =  106  g/mol
  • molar mass  of H2O=   (1 x2)  +16=  18 g/mol

   =  moles of Na2CO3  therefore= 0.786  g/106 g/mol= 0.00742  moles

        moles  of  H2O  =  1.337 g/18  g/mol =0.0743  moles


Step  3: find the mole  ratio

  •   that is  divide each mole by smallest  number of mole (0.00742)

= for  Na2CO3  = 0.00742/0.00742  =1

    for   H2O=  0.0743/0.00742 =  10

hence the value of X =10

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