## E 15

Seraphina Joseph 1C
Posts: 45
Joined: Wed Sep 30, 2020 9:31 pm

### E 15

How do you find the molar mass of sulfide in M(OH)2? And how do you know there is sulfide in M(OH)2?

Chem_Mod
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### Re: E 15

Seraphina Joseph 1C wrote:How do you find the molar mass of sulfide in M(OH)2? And how do you know there is sulfide in M(OH)2?

Hi Seraphina, it seems like you may have misinterpreted the problem. M(OH)2 is a metal hydroxide. Since you are given its molar mass and you know the molar masses of O and H from the periodic table, you can find the molar mass of the metal M. If you look at the metals in the periodic table you should then be able to identify what element M is. The second part of the question asks you to find the molar mass of the sulfide of this metal. Hint: M is a metal that forms an ion with a 2+ charge, so its sulfide would have the formula unit MS.

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### Re: E 15

Hi! The goal of this problem is to find what the element "m" is.
The problems tells us the molar mass of the metal hydroxide which is 74.10 g/mol. With this, we know that the molar mass of some element (we will call this x) + the molar mass of hydroxide (with a subscript of 2) = 74.10 g/mol. After a simple calculation, we find the molar mass of the unknown metal to be 40.084 g/mol. When we look at the periodic table, the element that has this molar mass is Calcium. Therefore, we know M. With this, we can then solve the second part of the problem which asks to find the molar mass of the metal sulfide. Hence, we have CaS, and we would simply find the molar mass of this.
Hope this helps!

Seraphina Joseph 1C
Posts: 45
Joined: Wed Sep 30, 2020 9:31 pm

### Re: E 15

I understand now Thank you both so much!