The molar mass of a compound is 88 g/mol. It contains 54.53% carbon, 9.15% hydrogen and 36.32% oxygen. What is the molecular formula of the compound?

Question

Naomi Aronson · Accepted Answer

#"C"_4"H"_8"O"#

When the compound's molar mass is known, one tactic is to choose a sample equivalent to one mole and utilize it to determine the molecular formula without first determining the empirical formula.

In this case, a molar mass of #"88 g mol"^(-1)# tells you that one mole of this compound has a mass of #"88 g"#.

Use the percent composition of the compound to determine how many grams of each element you'd get in this #"88-g"# sample. Remember, you can convert between percentages and grams by using a sample of #"100 g"#.

Consequently, you will have

#"For C: " 88color(red)(cancel(color(black)("g sample"))) * "54.53 g C"/(100color(red)(cancel(color(black)("g sample")))) = "47.986 g C"#

#"For H: " 88color(red)(cancel(color(black)("g sample"))) * "9.15 g H"/(100color(red)(cancel(color(black)("g sample")))) = "8.052 g H"#

#"For O: " 88 color(red)(cancel(color(black)("g sample"))) * "36.32 g O"/(100color(red)(cancel(color(black)("g sample")))) = "31.962 g O"#

Now find out how many moles of each element there are in one mole of this compound using the molar mass of each element.

#"For C: " 47.986color(red)(cancel(color(black)("g"))) * "1 mole C"/(12.011color(red)(cancel(color(black)("g")))) = 3.995 ~~ "4 moles C"#

#"For H: " 8.052color(red)(cancel(color(black)("g"))) * "1 mole H"/(1.00794color(red)(cancel(color(black)("g")))) = 7.990 ~~ "8 moles H"#

#"For O: " 31.962 color(red)(cancel(color(black)("g"))) * "1 mole O"/(15.9994color(red)(cancel(color(black)("g")))) = 1.998 ~~ "2 moles O"#

One mole of this compound contains these many moles of each element, so you can say that one molecule of the compound will contain

As a result, the molecular formula of the compound, which indicates the precise number of atoms of each element that make up a single molecule of the compound, will be

#color(green)("C"_4"H"_8"O"_2)#

Xavier Avery · Answer

undefined The compound's molecular formula is C3H2O₂.