What is the molecular formula of a compound that has a molecular mass of 54 and the empirical formula C2H3?

1 Answer
Meave60 · Truong-Son N.
May 23, 2017

The molecular formula is #"C"_4"H"_6"#.

Refer to the explanation for the process.

Explanation:

You have been given the empirical formula for a hydrocarbon. You need to determine the empirical formula mass. Then divide the molecular mass by the empirical mass. Then multiply the subscripts of the empirical formula by the result.

#color(blue)("Empirical Mass of C"_2"H"_3"#
Multiply the subscript of each element by its atomic mass and add.

#"C"_2"H"_3:##(2xx12.011"u C") + (3xx1.008 "u H")="27.046 u C"_2"H"_3"#

#color(blue)("Determine Molecular Formula"#
Divide the molecular mass by the empirical mass.

#54/(27.046)=2.0# rounded to two sig figs.

Multiply the subscripts in the empirical formula by 2 to get the molecular formula.

#""C_(2xx2)""H_(3xx2)"=C"_4"H"_6"#

The molecular formula is #"C"_4"H"_6"#.

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