Final answer:
Using the mass percentage and mole ratio, the empirical formula can be derived to determine the identity of element X, which is likely Boron (B) based on the calculated atomic mass of approximately 10.72 g/mol.
Step-by-step explanation:
To determine the identity of element X in a compound composed only of element X and hydrogen, we can examine the compound's percent composition and use the information provided regarding the mass and number ratio. Given that the compound is 78.14% element X by mass and that for every X atom, there are 3 hydrogen atoms, we can deduce the empirical formula of the compound.
Let's assume we have 100 g of the compound. This would mean we have 78.14 g of element X and 21.86 g of hydrogen. Since the atomic mass of hydrogen is approximately 1 g/mol, we can convert the mass of hydrogen to moles, giving us 21.86 moles of hydrogen. Because there are 3 times as many hydrogen atoms as X atoms, we can divide the moles of hydrogen by 3 to find the moles of X, which gives us approximately 7.29 moles of X.
To find the molar mass of X, we then divide the mass of X (78.14 g) by the moles of X (7.29 mol) to get approximately 10.72 g/mol. Consulting the periodic table, we find that the element closest to this atomic mass is Boron (B) with an atomic mass of approximately 10.81 g/mol. Therefore, element X is likely Boron (B).