Chemistry
Chemistry
Problem
A metal oxide with the empirical formula XO is found to contain 47.1\,% oxygen by mass. Chemists wish to determine the identity of element X and to rationalize the charge on X in the oxide lattice. (a) Calculate the atomic mass of X from the given mass percent composition. (b) Use the calculated atomic mass to identify the element X. (c) Predict the sign and magnitude of the ionic charge carried by X in XO, and explain how this prediction is consistent with the group number of the element. (d) Discuss how the stoichiometry of XO supports the concept of charge neutrality in ionic compounds, making specific reference to the oxide anion.Intuitive explanation
The key is using the oxygen percentage to find the actual molar mass of the compound, then working backward to identify element X. Since you know the empirical formula and that oxygen makes up 47.1% by mass, you can set up a ratio: the mass of oxygen in one formula unit divided by the total molar mass equals 0.471. Once you solve for the molar mass, compare it to multiples of the empirical formula mass to see if the compound is , , or another multiple—this tells you which element X is. Then the charge on X follows naturally from its position in the periodic table and the need to balance the oxide's overall neutrality.
Intuitive explanation
The key is using the oxygen percentage to find the actual molar mass of the compound, then working backward to identify element X. Since you know the empirical formula and that oxygen makes up 47.1% by mass, you can set up a ratio: the mass of oxygen in one formula unit divided by the total molar mass equals 0.471. Once you solve for the molar mass, compare it to multiples of the empirical formula mass to see if the compound is , , or another multiple—this tells you which element X is. Then the charge on X follows naturally from its position in the periodic table and the need to balance the oxide's overall neutrality.