At elevated temperature, NaHCO3 is concerted quantitatively to Na2CO3. Ignition o a 0.3592 g sample of an antacid tablet containing NaHCO3 ?

And non volatile impurities yielded a residue weighing 0.2362 g. Calculate the % purity of the NaHCO3 sample.

Molar mass= 

2NaHCO3(s)_>Na2CO(s)

84.01g/mol<_105.99g/mol

+ CO2(g)        + H2O(g)

    44.01g/mol  18.015g

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  • 2 months ago
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    (0.3592 g total) - (0.2362 g solids) = 0.123 g CO2 & H2O gases

    2 NaHCO3(s) → CO2(g) + H2O(g) + Na2CO3(s)

    CO2 and H2O are produced in equal numbers of moles, so they can be considered as a single compound, CH2O3.

    (0.123 g CH2O3) / (62.0248 g CH2O3/mol) x (2 mol NaHCO3 / 1 mol CH2O3) x

    (84.0066 g NaHCO3/mol) / (0.3592 g total) = 0.9276 = 92.76% NaHCO3 by mass

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