The empirical formula of a compound is the simplest whole number ratio of the elements present in the compound. To determine the empirical formula, we need to find the ratio of the masses of the elements present.

Given that the compound contains 75.7% arsenic and 24.3% oxygen, we can assume that we have 100g of the compound. This means that we have 75.7g of arsenic and 24.3g of oxygen.

To find the ratio of the masses, we divide the mass of each element by its atomic mass. The atomic mass of arsenic (As) is 74.923g/mol and the atomic mass of oxygen (O) is 16.00g/mol.

Mass of arsenic (As) = 75.7g / 74.923g/mol = 1.01 moles

Mass of oxygen (O) = 24.3g / 16.00g/mol = 1.52 moles

Now, we divide both moles by the smaller number of moles to get the simplest whole number ratio.

Dividing by 1.01 moles:

As: 1.01 moles / 1.01 moles = 1

O: 1.52 moles / 1.01 moles ≈ 1.5

To get whole numbers, we can multiply both numbers by 2:

As: 1 x 2 = 2

O: 1.5 x 2 ≈ 3

Therefore, the empirical formula of the compound is As2O3.