1.67 x 10^-3 moles
Calculate the molar mass of C9H8O4
Carbon = 12.0107
Hydrogen = 1.00794
Oxygen = 15.999
C9H8O4 = 9 * 12.0107 + 8 * 1.00794 + 4 * 15.999 = 180.1558
Now divide the mass you have by the molar mass
0.300 g / 180.1558 g/mole = 1.665225 x 10^-3
Round to 3 significant figures
1.67 x 10^-3
