# Chapter 2 Atoms, Molecules, and Ions - Study Questions - Page 95g: 120

a) $C_2H_6O_2$ $M=62.07\ g/mol$ b) $C_3H_6O_3$ $M=90.08\ g/mol$ c) $C_6H_8O_6$ $M=176.12\ g/mol$ The molecule with the largest mass percents of both carbon and oxygen is ascorbic acid.

#### Work Step by Step

Atomic weights: $C: 12.011,\ H: 1.0079,\ O: 15.999$ a) $C_2H_6O_2$ $M=2\times12.011+6\times1.0079+2\times15.999=62.07\ g/mol$ Mass percents: C: $2\times12.011/62.07\times100\%=38.70\%$ O: $2\times15.999/62.07\times100\%=51.55\%$. b) $C_3H_6O_3$ $M=3\times12.011+6\times1.0079+3\times15.999=90.08\ g/mol$ Mass percents: C: $3\times12.011/90.08\times100\%=40.00\%$ O: $3\times15.999/90.08\times100\%=53.28\%$ c) $C_6H_8O_6$ $M=6\times12.011+8\times1.0079+6\times15.999=176.12\ g/mol$ Mass percents: C: $6\times12.011/176.12\times100\%=40.92\%$ O: $6\times15.999/176.12\times100\%=54.51\%$ The molecule with the largest mass percent of both carbon and oxygen is ascorbic acid.

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