We’re being asked to determine the mass % C in the sample.
Recall that in combustion analysis, a compound reacts with excess O2 to form products. For a compound composed only of C and H, the reaction looks like this:
CxHy + O2 (excess) → x CO2 + y/2 H2O
This means we need to do the following steps:
Step 1: Calculate the moles of C in the compound.
Step 2: Calculate the mass of C.
Step 3: Calculate the mass % of C in the sample.
A hydrocarbon sample with a mass of 6.0 grams underwent combustion to produce 11.0 grams of carbon dioxide. If all the carbon initially present in the compound was converted to carbon dioxide, what was the percent of carbon, by mass, in the hydrocarbon sample?