PART - 2 CH - 8 Organic Chemistry: Some Basic Principles and Techniques — Chemistry STD 11 Science — Question
Gujarat BoardEnglish MediumSTD 11 ScienceChemistryPART - 2 CH - 8 Organic Chemistry: Some Basic Principles and Techniques2 Marks
Question
Write the method of analysis of oxygen in organic compounds.
✓
Answer
The percentage of oxygen in an organic compound is usually found by difference between the total percentage composition (100) and the sum of the percentages of all other elements. However, oxygen can also be estimated directly as follows : A definite mass of an organic compound is decomposed by heating in a stream of nitrogen gas. The mixture of gaseous products containing oxygen is passed over red-hot coke when all the oxygen is converted to carbon monoxide. This mixture is passed through warm iodine pentoxide $\left( I _2 O _5\right)$ when carbon monoxide is oxidised to carbon dioxide producing iodine. $\begin{array}{l} \left.2 C+O_2 \xrightarrow{1373 K} 2 CO\right] \times 5......(i) \\ \left.I_2 O_5+5 CO \longrightarrow I_2+5 CO_2\right] \times 2.......(ii) \end{array}$ On making the amount of CO produced in equation (i) equal to the amount of CO used in equation (ii) by multiplying the equations (i) and (ii) by 5 and 2 respectively; we find that each mole of oxygen liberated from the compound will produce two moles of carbon dioxide. Thus 88 g carbon dioxide is obtained if 32 g oxygen is liberated. Calculation : Let the mass of organic compound taken be mg Mass of carbon dioxide produced be $m _1 g$ $\therefore m _1 g$ carbon dioxide is obtained from $\frac{32 \times m _1}{88} g O _2$ $\therefore$ Percentage of oxygen $=\frac{32 \times m _1 \times 100}{88 \times m } \%$
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