Question

1.00 g of a compound is combusted in oxygen and found to give 3.14g of CO2 and 1.29 g of H2O. From these data we can tell thatA. the compound contains C, H, and some other element of unknownidentity, so we can’t calculate the empirical formula.B. the compound contains only C and H and has the empirical formulaof C6H.C. the compound contains C, H, and O and has the empirical formulaof CH3O.D. the compound contains only C and H and has the empirical formulaof CH2.E. None of the above is a true statement

Answer 1

the compound contains C, H, and some other element of unknownidentity, so we can’t calculate the empirical formula

Step-by-step explanation:

Mass of CO2 obtained = 3.14 g

Hence number of moles of CO2 = 3.14g/44.0 g = 0.0714 mol

The mass of the carbon in the sample = 0.0714 mol × 12.0g/mol = 0.857 g

Mass of H2O obtained = 1.29 g

Hence number of moles of H2O = 1.29g/18.0 g = 0.0717 mol

The mass of the carbon in the sample = 0.0717 mol × 1g/mol = 0.0717 g

% by mass of carbon = 0.857/1 ×100 = 85.7 %

% by mass of hydrogen = 0.0717/1 × 100 = 7.17%

Mass of carbon and hydrogen = 85.7 + 7.17 = 92.87 %

Hence, there must be an unidentified element that accounts for (100 - 92.87) = 7.13% of the compound.