Molar Mass and Metal/Sulfides

[Matt Jacobs 3H]

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?
Can someone please explain what the sulfide of a metal is, and how it's molar mass differs from the metal. Thanks.

[Marla Dimetrios 3J]

This question has two parts:
1) you need to figure out the mystery metal and you can do so by subtracting the mass of the hydrogen and the oxygens from the molar mass given
74.10 - ( 2x1.008+2x15.999) =39.94 g/mol
if you look on the periodic table you will find that the closest element that that molar mass is Calcium
2) using Calcium ( the mystery metal ) you just found, solve for the molar mass of metal sulfide
in this case calcium sulfide so 40.078+32.05=72.13

[Leyla Anwar 3B]

Hi, where does the 32.05 come from? Is that how to make any metal a sulfide? Or is that specific to Ca?

[haley f]

Hi, where does the 32.05 come from? Is that how to make any metal a sulfide? Or is that specific to Ca?

I was wondering the same thing! Here's what I found: Calcium sulfide is Ca and S so the 32.05 is simply the molar mass of sulfur!

[Sophia Spungin 2E]

Basically, this question wants you to solve for the molar mass of 'M' and identify it by finding the correct element on the periodic table with this molar mass. You do this by subtracting the molar mass of the known elements from the total molar mass.

Looking at the periodic table, M is revealed to be Ca.

Then, the suffix sulfide indicates S^2. Using this, you simply find the molar mass of CaS^2
[img]Messages%20Image(4121047214).jpeg[/img]

Here is a list of common ions

[705573518]

Basically, this question wants you to solve for the molar mass of 'M' and identify it by finding the correct element on the periodic table with this molar mass. You do this by subtracting the molar mass of the known elements from the total molar mass.

Looking at the periodic table, M is revealed to be Ca.

Then, the suffix sulfide indicates S^2. Using this, you simply find the molar mass of CaS^2
[img]Messages%20Image(4121047214).jpeg[/img]

Here is a list of common ions

This is super helpful. Just to clarify though, once you determine calcium, you disregard the H and O molecular weights in the final calculation and just do CaS2??

[sadiebrebes]

This question has two parts:
1) you need to figure out the mystery metal and you can do so by subtracting the mass of the hydrogen and the oxygens from the molar mass given
74.10 - ( 2x1.008+2x15.999) =39.94 g/mol
if you look on the periodic table you will find that the closest element that that molar mass is Calcium
2) using Calcium ( the mystery metal ) you just found, solve for the molar mass of metal sulfide
in this case calcium sulfide so 40.078+32.05=72.13

Why 40.078? Shouldn't it be 39.94, which we just calculated?

[Nathalia Garibay 1D]

Hi! I Believe that she may just have ended up rounding the 39 to 40 to make it easier to calculate. Hope this helps.

[Nathalia Garibay 1D]

This question has two parts:
1) you need to figure out the mystery metal and you can do so by subtracting the mass of the hydrogen and the oxygens from the molar mass given
74.10 - ( 2x1.008+2x15.999) =39.94 g/mol
if you look on the periodic table you will find that the closest element that that molar mass is Calcium
2) using Calcium ( the mystery metal ) you just found, solve for the molar mass of metal sulfide
in this case calcium sulfide so 40.078+32.05=72.13

Why 40.078? Shouldn't it be 39.94, which we just calculated?

I think what she did was get the actual mass of Calcium from the periodic table. Hope this helps!