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Author Topic: HELP WITH CHEMISTRY QUESTION?  (Read 4279 times)

Offline Xule

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HELP WITH CHEMISTRY QUESTION?
« on: 09/10/2006 20:30:00 »
ok, i almost got the value for X, when i realised a problem with my figures. i got total molar mass for Na2CO3.xH2O as 106.08.[?]

QUESTION: an experiment was carried out to determine the %water crystallisation and the degree of water crystallisation,
  • , in a sample of hydrated sodium carbonate crystals [Na2CO3.xH2O]. an 8.2g sample of the crystals was weighed accurately on a clock glass and then made up to 500cm3 of solution in a volumetric flask. A pipette was used to transfer 25cm3 portions of this solution to a conical flask. a previously standardised 0.11M hydrochloric acid solution was use to titrate each sample. a number of accurate titratons were carried out. the average volume of hydrochloric acid solution required in these titrations was 26.05cm3


REACTION: Na2CO3 + 2HCl - 2NaCl + CO2 + H2O

can you help me figure out what i got wrong?
[V]

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Offline lightarrow

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Re: HELP WITH CHEMISTRY QUESTION?
« Reply #1 on: 10/10/2006 14:13:08 »
26.05*0.11 = 2.8655 millimoli HCl (=2.87*10^-3 mol HCl)

2.8655/2 = 1.4328 millimol Na2CO3

1.4328/25 = 0.05731 mol/L Na2CO3

0.05731*0.500 = 0.028655 mol Na2CO3

0.028655*106 = 3.037 grams Na2CO3

8.2 - 3.037 = 5.1626 grams H2O

5.1626/18 = 0.2868 mol H2O --> x = 10:

Na2CO3*10H2O
« Last Edit: 12/10/2006 15:07:28 by lightarrow »
 

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Re: HELP WITH CHEMISTRY QUESTION?
« Reply #1 on: 10/10/2006 14:13:08 »

 

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