1. The problem statement, all variables and given/known data An unknown compound weighs 1.023 kg. It is known that element X composes 28.3% of the compound. Given that the molar mass is 240.5 g/mol, find element X. 2. Relevant equations mole = mass / atomic weight (n = m / Ar) mole = mass / molecular weight (n = m / Mr) mole = number of particles / Avogadro's number (n = P / NA) 3. The attempt at a solution I tried solving using the first equation, but I don't know them mass, Ar or mole of element X. I solved for the mole of the substance using the second equation, but I don't know how to find the unknown element from there. I don't think the last equation is applicable in this particular case, but I included it just in case.