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Washing soda is a hydrate of sodium carbonate. Its formula is Na2CO3 X xH20. A 2.714 g sample of washing soda is heated until a constant mass of 1.006 of Na2CO3 is reached. What is x? What is the experimental mass percent of water in the hydrate?

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  1. 2.714-1.006 = 1.708 g = mass water released upon heating.
    Convert grams to moles.
    moles wash soda = 1.006/106 = ??
    moles H2O = 1.708/18.015 = ??
    Now find the ratio of the two numbers to each other. The easy way to do that is to divide the smaller number by itself (which assures you of getting 1.000 for that number). Then divide the other number by the same small number and round to a whole number. That will give you (Na2CO3)1.xH2O; i.e., x will be the number of H2O molecules in ONE mole Na2CO3.

    For percent water, (grams water/grams compound)*100 = ??

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