Gravimetric analysis
Chemistry
Level
3
- at elevated temperature, NaHCO3 (83.98g/mol) is converted quantitatively to Na2CO3 (105.98g/mol).Ignition of 0.3592g sample of an antacid tablet containing NaHCO3 and non volatile impurities yielded a residue weighing 0.2362g. Calculate the percent purity of the sample.
The answer is 92.2.
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1 solution
The 0.2362 g here is the mass of the nonvolatile impurities. So to get the mass of the volatilized part of the tablet, subtract 0.2362 from the given mass of the tablet 0.3592. Thus, 0.1230 g. Since it said there that 0.2362 is the mass of the impurities, the mass that we just solved is the pure NaHCO3. All we need to do is to convert that mass to NaHCO3 and divide it by the original mass of the sample.
%NaHCO3= {[combined mass of CO2 and H2O x ((2NaHCO3)/(CO2+H20))] / g sample} x 100 = {[.1230 x ((2 x 84.01)/ ( 44.01 + 18.02 ))] / 0.3592 } x 100 = 92.75%