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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» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :`Na_2CO_3` does not decompose at the given temperature. It is only `NaHCO_3` which decomposes at this temperature. The corresponding equation is:<br/> `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` <br/> `CO_(2)` and `H_(2)O` scape as gases and cause a loss in mass. <a href="https://interviewquestions.tuteehub.com/tag/total-711110" style="font-weight:bold;" target="_blank" title="Click to know more about TOTAL">TOTAL</a> mass of `CO_2 + H_2O` (loss in mass)<br/> =44.01 + 18.016 = 62.026 g<br/> As according to the above equation,`therefore 0.248` g mass is <a href="https://interviewquestions.tuteehub.com/tag/lost-537630" style="font-weight:bold;" target="_blank" title="Click to know more about LOST">LOST</a> by `NaHCO_3 = 168.016` g <br/> `therefore 0.248`gmasswillbelostby`NaHCO_(3) = (168.016)/(62.026) xx 0.248 = 0.672 g` <br/> Since, the total mass of the sample is 2.0 g, the mass of `Na_2CO_3` <a href="https://interviewquestions.tuteehub.com/tag/present-1163722" style="font-weight:bold;" target="_blank" title="Click to know more about PRESENT">PRESENT</a> in it = `2.0 - 0.672 = 1.328 g` <br/> `therefore` <a href="https://interviewquestions.tuteehub.com/tag/percentage-13406" style="font-weight:bold;" target="_blank" title="Click to know more about PERCENTAGE">PERCENTAGE</a> of `Na_(2)CO_(3) = (1.328)/2 xx 100 = 66.4` <br/> Hence, the given sample contains `66.4% Na_(2)CO_(3)`.</body></html>


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