During its combustion, ethane combines with oxygen to give carbon dioxide and water. A sample of ethane was burned completely and the water that formed has a mass of 1.61 grams. How many grams of ethane were in the sample?

Answer 1

2C2H6 + 7O2 ==> 4CO2 + 6H2O

mols H2o formed = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols H2O to mols ethane.
Now convert mols ethane to grams; grams = mols ethane x molar mass ethane.