For the purpose of proper representation in this item, we let the number of moles of carbon in the compound be x, that of H is y. The equation of toluene now becomes,
CxHy
The combustion reaction is,
CxHy + O2 --> CO2 + H2O
The equation presented above may not be balanced yet. Then, we determine the number of mmols of C, H, and O in the product using the given masses.
(1) 8.20 mg CO2
(8.2 mg CO2)(1 mmol CO2/44 mg CO2) = 0.186 mmol CO2
which means,
0.186 mmol C
0.373 mmol O
(2) 1.92 mg H2O
(1.92 mg H2O)(1 mmol H2O/18 mg H2O) = 0.107 mmol H2O
which means
0.2133 mmol H
0.107 mmol O
Thus, the equation for toluene is,
C(0.186)H(0.2133)
Dividing the numbers by the lesser value,
CH(8/7)
To eliminate the fraction, we multiply by the denominator. Thus, the final answer would be,
<em> C7H8</em>
