Carbon dioxide has a molecular weight of 44.01 grams per mole.
Water has a molecular weight of 18.015 grams per mole.
Divide the number of grams by the molecular weight to get the number of moles
1.60/44.01 = 0.036355 moles, or 36.355 millimoles carbon dioxide. Each carbon dioxide molecule contains one carbon atom, so this represents 36.355 millimoles of carbon
0.819/18.015 = 0.045462 moles, or 45.462 millimoles water. Each water molecule contains two hydrogens, so this represents 90.924 moles of hydrogen.
The ratio of hydrogen to carbon is 90.924/36.355 = 2.50. This means there are 2.5 hydrogen atoms to each carbon atom. Multiply by 2 to get a ratio of 5 hydrogens to 2 carbons. The empirical formula is therefore