a compound contains only carbon, oxygen, hydrogen. A 5.000 g sample of the compound is combusted and 6.638 L of carbon dioxide ( 1.15 atm and 298 K) and 5.621 of water are produced . The molecular weight of the compound is app 128 g/mol. Determine the molecular formula of the compound.

Question

jfraser · Answer

use the ideal gas law to find moles of $CO_2$ produced. Use the mass percent of C in $CO_2$ to find the mass of C that came from the sample. Do the same thing with the water. The rest of the 5.00g sample must come from the oxygen.

Once you have a mass of each element, C, H, and O, convert to moles, then divide by the smallest to find a whole # mole ratio. The molecular formula will be a whole # multiple of the lowest whole # ratio, so that the ratio $\frac{MF}{EF}$ is a small whole #.