## E.15 homework question [ENDORSED]

kennedy_meyer_
Posts: 3
Joined: Fri Sep 29, 2017 7:04 am

### E.15 homework question

Where did the calcium that is part of the answer in the solutions manual come from? Is it just another example of a compound that includes sulfide?

Riya Pathare 2E
Posts: 74
Joined: Sat Jul 22, 2017 3:01 am
Been upvoted: 1 time

### Re: E.15 homework question

The M in the M(OH)2 represents a metal, not a particular element, so the problem wants you to find the metal that M represents, given the molar mass. If you subtract out the weight of (oh)2 from the molar mass you will get the mass of Ca which is what the M represents in the problem. Then you just find the sulfide of Ca.

Andrea ORiordan 1L
Posts: 52
Joined: Fri Sep 29, 2017 7:04 am
Been upvoted: 2 times

### Re: E.15 homework question

Dr. Lavelle also said that he would go over the naming of compounds- and we'll probably go over oxidation numbers too. So don't worry if you don't automatically know the formula of calcium sulfide.

Paula Dowdell 1F
Posts: 72
Joined: Tue Nov 15, 2016 3:00 am

### Re: E.15 homework question

I had the same problem! Just note that the question says "metal hydroxide". You can assume that M=metal and hydroxide= (OH)2.

Chem_Mod
Posts: 18400
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 435 times

### Re: E.15 homework question  [ENDORSED]

Correct I will cover oxidation states in several parts of Chem 14A, even though it is high-school chem.

Subtract the mass of the two -OH from the given mass.
The remaining mass is the metal, M.
Then look at the periodic table for a metal with that mass and you will see it matches calcium.

Hope this helps.