Percent Composition Answers for Part Two


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1) Benzene, C6H6

Molar mass = 78.11 g/mol
Carbon: ((6 x 12.011) / 78.11) x 100 = 92.26%
Hydrogen: ((6 x 1.008) / 78.11) x 100 = 7.74%

2) Acetylene, C2H2

Molar mass = 26.04 g/mol
Carbon: ((2 x 12.011) / 26.04) x 100 = 92.25%
Hydrogen: ((2 x 1.008) / 26.04) x 100 = 7.75%

Please note that, within reasonable limits, the percentage compositions are the same for benzene and acetylene. This is because they both have the same empirical formula, which is the lowest whole-number ratio of atoms in a molecule. Both substances have a 1:1 ratio of carbon to hydrogen.

3) C7H16

We know that all nine compounds with this empirical formula will have the same percentage composition, which is: C = 89.30%, H = 10.7%.

4 and 5) If you find definitions quite different from mine, I'd like to see them.

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