We can determine the empirical formula by first converting each of the grams to moles. remember to do this, first, we need the molar mass of the molecules which can be calculated by adding the mass of the atoms from the periodic table.
molar mass of CO2= 44.0 g/mol molar mass of H2O= 18.02 g/mol
now, lets determine the grams of each atom
Carbon: 23.98 g x (12.011 g / 44.01 g) = 6.54 g C
Hydrogen: 4.91 g x (2.0158 g / 18.02 g) = 0.55 g H
Oxygen: 10.0 - (6.54 + 0.55) = 2.91 g O
Now let's convert each mass to moles.
C: 6.54 g / 12.01 g / mol = 0.54 mol H: 0.55 g / 1.01 g/mol = 0.54 mol O: 2.91 g / 16.00 g/mol = 0.18 mol
now that we have the moles of each atom, we need to divide them by the smallest value to find the ration. If you do not get the whole number, you need to multiply until to get a whole number.
