A compound is 38.77% Cl and 61.23% O

Answer 1

38.77% Cl and 61.23% O
I don't see a question here but I assume you want the empirical formula.
Take a 100 gram sample which will give you 38.77 g Cl and 61.23 g O.
Convert to moles. moles = g/atomic mass
moles Cl atoms = 38.77/35.5 = 1.09 (rounded)
moles O atoms = 61.23/16 = 3.83 (rounded)
You want to find the ratio of the atoms to each other with them being whole numbers and the smaller being no less than 1.00. The easy way to do this is to divide both by the smaller of the two; i.e.,
mols Cl atoms = 1.09/1.09 = 1.00
mols O atoms = 3.83/1.09 = 3.52 (rounds to 3.50)
We can't write Cl1.0O3.5 but that O part is not a whole number BUT we can see that doubling them will give you Cl2.0O7.0 as whole numbers so we write the empirical formula as Cl2O7