Molar Mass of Sulfide

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Noh_Jasmine_1J
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Joined: Fri Sep 28, 2018 12:15 am

Molar Mass of Sulfide

Postby Noh_Jasmine_1J » Sun Sep 30, 2018 8:51 pm

Hi I have a question on E.15 (7th edition). It gives me the molar mass of a metal oxide M(OH)2 as 74.10 g/mol and asks me to find the molar mass of the sulfide. How do I make the connection between sulfide and (OH)2?

Christopher Tran 1J
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Joined: Fri Sep 28, 2018 12:15 am

Re: Molar Mass of Sulfide

Postby Christopher Tran 1J » Sun Sep 30, 2018 9:07 pm

The question first wants you to determine the metal "M" in M(OH)2 with molar mass 74.10 g/mol, which we can find by finding the molar mass of "M."

(OH)2 has molar mass: (16.00+1.01)*2 = 34.02 g/mol

Molar mass of "M" in M(OH)2 = 74.10 g/mol - 34.02 g/mol = 40.08 g/mol

Looking at the periodic table, the metal that has a molar mass most similar to 40.08 g/mol is calcium (Ca).

So the mystery metal "M" is Ca, and the question wants you to find the sulfide of this metal.

Sulfides have the ion S2-, so the sulfide of the metal calcium is CaS (calcium sulfide). From there, you can calculate the molar mass!


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

Nada AbouHaiba 1I
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Joined: Fri Sep 28, 2018 12:28 am
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Re: Molar Mass of Sulfide

Postby Nada AbouHaiba 1I » Sun Sep 30, 2018 9:10 pm

I found the answer to this question on an earlier post and I believe they did a good job of explaining it! I'll go ahead and link it below :)

viewtopic.php?t=5565


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