Textbook Problem E.15 [ENDORSED]

[MHarrold_1E]

Could someone walk me through the steps to solve this problem...

The molar mass of the metal hydroxide M(OH)2 is 74.10 g/mol. What is the molar mass of the sulfide of this metal?

[Sophia Hu 1A]

Since you know (OH)2 is part of the metal hydroxide you can find that molar mass which is 34.02 grams/mol. You are given that teh entire metal hydroxide molar mass is 74.10 grams/mol.

74.10 grams/mol - 34.02 grams/mol = 40.08 grams/mol

This molar mass is the molar mass of Ca.

Therefore, the metal hydroxide would be Ca(OH)2

The problem asks you to find the molar mass of the sulfide of this metal: CaS

40.08 grams/mol + 32.06 grams/mol = 72.14 grams/mol of CaS

[Samudrala_Vaishnavi 3A]

To put it simply, this problem is asking you to basically find a type of metal, add sulfur to that metal, and then find the molar mass of that metal and the sulfur.
1.) subtract the molar masses of hydrogen and oxygen from the total molar mass given.
2.) find an element on the periodic table that has the same/ closest molar mass to what you found from subtraction in Step 1.
3.) Add a sulfate to this.
4.) Calculate the molar mass of element found and the sulfate. (Add together since they are a compound)

[Thomas Gimeno]

Well the first step is to identify what the sulfide would look like. Because Ca would give up its two valence electrons it has a charge of +2. Sulfur wants to gain two electrons to fill its outer shell which makes it -2. This means the Calcium Sulfide is just CaS. To then find the molar mass you can just add the molar mass of calcium to that of sulfer.

40.08g/mol+32.06g/mol=72.14g/mol