Answer:
To calculate the percent composition, we need to know the masses of C, H, and O in a known mass of C9H8O4. It is convenient to consider 1 mol of C9H8O4 and use its molar mass (180.159 g/mole, determined from the chemical formula) to calculate the percentages of each of its elements:
%
C
9
mol C
×
molar mass C
molar mass
C
9
H
18
O
4
×
100
=
9
×
12.01
g/mol
180.159
g/mol
×
100
=
108.09
g/mol
180.159
g/mol
×
100
%
C
60.00
%
C