Finding the Sulfide of a Metal

[alexia11]

How would I go about finding the sulfide of a metal when given the molar mass of the metal hydroxide? Specifically, for the question E15 on the syllabus practice problems.

[Ashely_Pavon_2E]

First I think you would have to subtract the molar mass of the hydroxide from the molar mass you were initially given. Then you would add the molar mass of that metal and the molar mass of sulfur to the molar mass of the metal.

[Ahjin Kim 2B]

Since we know the total molar mass, we can subtract the molar mass of the known elements (OH)2 from the total mass to get the molar mass of the metal. This will give us 74.1 - 34.014 = 40.086 as the molar mass of the unknown metal, which is closest to calcium (as found on the ptable). From there, calcium sulfide (CuS)'s molar mass can be found --- 40.086 + 32.06 = 72.146 g/mol