HW E.15

Moderators: Chem_Mod, Chem_Admin

Lucy Wang 2J
Posts: 86
Joined: Wed Sep 30, 2020 10:09 pm
Been upvoted: 2 times

HW E.15

Postby Lucy Wang 2J » Fri Oct 09, 2020 3:04 pm

E.15 The molar mass of the metal hydroxide M(OH)2 is 74.10g*mol -1. What is the molar mass of the sulfide of this metal?

What does it mean the sulfide of this metal? Am I supposed to convert it to something else?

Shanna Yu 1C
Posts: 101
Joined: Wed Sep 30, 2020 9:36 pm
Been upvoted: 3 times

Re: HW E.15

Postby Shanna Yu 1C » Fri Oct 09, 2020 3:12 pm

Hi!

So first, you wanna figure out what the molar mass of the metal is (M). You can do this by subtracting the hydroxide's molar mass from the given molar mass (74.10 g/mol). This should give you 39.94 g/mol, which again, is the molar mass of the metal (M) in the compound.

If you look at the periodic table, the element with this molar mass is calcium.

The question asks for the sulfide of calcium, which is just CaS. Add the molar masses of calcium and sulfur together to get your answer! Lemme know if you have any questions.

rachelhchem1I
Posts: 97
Joined: Wed Sep 30, 2020 10:06 pm

Re: HW E.15

Postby rachelhchem1I » Fri Oct 09, 2020 3:15 pm

So a "sulfide" is a compound containing one or more S²⁻ ions. Therefore, you are supposed to figure out what the mystery medal is in M(OH)2, then using this metal, figure out its molar mass when paired with a sulfur ion. In this case the metal in the hydroxide is Ca, then you just find the molar mass of CaS. Hope this helps!!

Colin Squire 3B
Posts: 90
Joined: Wed Sep 30, 2020 9:35 pm

Re: HW E.15

Postby Colin Squire 3B » Fri Oct 09, 2020 3:23 pm

The steps I took for this question was to first find out what M was equal to. I did that by finding the molar mass of the hydroxide (OH)2, which was 34.08g/mol, and subtracting it to the given molar mass, 74.10g/mol. The missing molar mass would be 40.08g/mol which is the exact same as calcium. For the sulfide part, its basically asking what the molar mass of calcium sulfide (CaS). Since Ca is 2+ charge and sulfide is 2-, they pair evenly without a change in subscripts. Finally, take the molar masses of calcium and sulfur and add them together to get the answer. Hope this helped !

Andrew Yoon 3L
Posts: 92
Joined: Wed Sep 30, 2020 9:36 pm

Re: HW E.15

Postby Andrew Yoon 3L » Sat Oct 10, 2020 8:01 pm

The first step that I took to solve this problem was to figure out the mass of M. Since we know the mysterious compound has a molar mass of 74.10 g/mol and the molar mass of (OH)2, we can figure out the molar mass of M by subtracting 34.08 g/mol from 74.10 g/mol. This mass turns out to be 40.08g/mol, which is the molar mass of calcium. Calcium has a 2+ charge while sulfur has a 2- charge. So, the formula would be CaS. Finally, to find the molar mass of the sulfide would be the addition of the molar masses of calcium and sulfur.

Hope this helps!


Return to “Accuracy, Precision, Mole, Other Definitions”

Who is online

Users browsing this forum: No registered users and 1 guest