Final answer:
By combining known masses of element X and oxygen we calculate the molar mass of X to be 80.00 amu, which does not match the provided answer choices, indicating a possible error in the options.
Step-by-step explanation:
To find the atomic mass of element X, we start by noting that 44.0 grams of X react with 8.00 grams of oxygen to form XO2. Given that the molecular mass of oxygen (O) is approximately 16.00 amu per atom, the total mass of oxygen in the compound is 2 x 16.00 amu = 32.00 amu. Now, to find the mass of one mole of the oxygen atoms that combine with X, we multiply the atomic mass by the number of atoms in one mole (Avogadro's number, 6.02 x 1023), yielding a molar mass of 32.00 g/mol for the oxygen in the compound.
The next step is to subtract the mass of the oxygen from the total mass of the XO2 compound (44.0 + 8.00 = 52.00 grams) to obtain the mass of element X in the compound, which is 52.00 g - 32.00 g = 20.00 g. Since we have the mass of oxygen in moles (8.00 g is 0.5 moles of O), and XO2 indicates there are 2 moles of O for every mole of X, there must be 0.25 moles of X present in 20.00 g.
Finally, to find the atomic mass of element X, we take the mass of element X (20.00 g) and divide it by the number of moles (0.25 moles), resulting in an atomic mass of 80.00 g/mol or 80.00 amu. Since none of the multiple-choice answers matches this value, it appears there may be an error in the options provided.