# Question #bc73f

Jan 15, 2014

Glucose is a 6 carbon molecule of ${C}_{6} {H}_{12} {O}_{6}$

The percent composition of carbon in the molecule is determined by comparing the mass of carbon in the molecule versus the total mass of the molecule.

To begin we need to find the molar mass (gram formula mass of the glucose molecule.

carbon has a mass of 12.01 amu (mass from the periodic table)
hydrogen has a mass of 1.01 amu
oxygen has a mass of 15.99 amu

C 6 x 12.01 = 72.06 (atom number x amu)
H 12 x 1.01 = 12.12
O 6 x 15.99 = 95.94

72.06 + 12.12 + 95.94 = 180.12 $\frac{g}{m o l}$

To determine the percent composition compare the mass of each element to the total mass of the molecule.

C $\frac{72.06}{180.12}$ = 0.400 or 40%

H $\frac{12.12}{180.12}$ = 0.067 or 6.7%

O $\frac{95.94}{180.12}$ = 0.533 or 53.3%

The percent composition of glucose is 40% carbon, 6.7% hydrogen and 53.3% oxygen.

Here are YouTube videos I made for percent composite and gram formula mass: