A 2.0 g sample containing Na_2CO_3 and NaHCO_3 loses 0.248 g when heated at 300° C, the temperature at which NaHC03 decomposes to Na_2CO_3, CO_2 and H_2O. What is the percentage of Na_2CO_3 in the mixture ?

A 2.0 g sample containing Na_2CO_3 and NaHCO_3 loses 0.248 g when heat

1.	A 2.0 g sample containing Na_2CO_3 and NaHCO_3 loses 0.248 g when heated at 300° C, the temperature at which NaHC03 decomposes to Na_2CO_3, CO_2 and H_2O. What is the percentage of Na_2CO_3 in the mixture ?
Answer» SOLUTION :`Na_2CO_3` does not decompose at the given temperature. It is only `NaHCO_3` which decomposes at this temperature. The corresponding equation is: `underset(168.016 g) (2NaHCO_(3)) overset(300^(@) C) to underset(44.01 g)(Na_(2)CO_(3)) + underset(18.016 g)(CO_(2)) + H_(2)O` `CO_(2)` and `H_(2)O` scape as gases and cause a loss in mass. TOTAL mass of `CO_2 + H_2O` (loss in mass) =44.01 + 18.016 = 62.026 g As according to the above equation,`therefore 0.248` g mass is LOST by `NaHCO_3 = 168.016` g `therefore 0.248`gmasswillbelostby`NaHCO_(3) = (168.016)/(62.026) xx 0.248 = 0.672 g` Since, the total mass of the sample is 2.0 g, the mass of `Na_2CO_3` PRESENT in it = `2.0 - 0.672 = 1.328 g` `therefore` PERCENTAGE of `Na_(2)CO_(3) = (1.328)/2 xx 100 = 66.4` Hence, the given sample contains `66.4% Na_(2)CO_(3)`.