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(i) Butyric acid contains only `C, H` and `O.A4.24 mg` sample of butyric acid is completely burned. It gives `8.45 mg` of carbon dioxide `(CO_(2))` and `3.46 mg` of water. What is the mass percentage of each element in butyric acid? (ii) If the elemental composition of butyric acid is found to be `54.2% C, 9.2% H` and `36.6%O`, determine the empirical formula. (iii) The molecular mass of butyric acid was determined of experiment to be `88`. What is the moleculare formula ? |
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Answer» (i) `%C(12xx8.45)/(44xx4.24)xx100= 54.35%` `%H=(2xx3.46)/(18xx4.24)xx100= 9.06%` `%O=[100-54.35-9.06]=36.59%` (ii) `|{:(%,%at.wt.="Factor","factor/Lower number"),(C=54.2,(54.2)/(12)=4.52,(4.52)/(2.29)=2),(H=9.2,(9.2)/(1)=9.2,(9.2)/(2.29)=4),(O=36.6,(36.6)/(16)=2.29,(2.29)/(2.29)=1):}:|` `:.` Empirical forumula of butyric acid is `C_(2)H_(4)O` (iii) Empirical formula mass `=44` Molecular mass `=88` `("Molecular mass")/("Empirical mass")=(88)/(44)=2` `:. "Molecular formula"="Empirical forumula"xxn` `=C_(4)H_(8)O_(2)` |
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