# Chemical Forums

## Chemistry Forums for Students => High School Chemistry Forum => Topic started by: iLoveScience_103 on August 16, 2012, 07:45:21 PM

Title: CaSx - What is this and how do I use it?
Post by: iLoveScience_103 on August 16, 2012, 07:45:21 PM
Hey guys,

I have been given a situational problem, and the teacher is not willing to help. He is always like that, he says its part of the learning experience.
Anyways, I am not out here to complain.

After several hours of research, I am still not able to understand what Casx is. (Calcium Polysulfide)

What I want to know is, what is this chemical? What is its atomic weight, density? How would I apply it to a chemical equation such as :

Hcl + Casx --> ?                What would the answer be, the closest I came to was Hcl + Cas -> H2S + CaCl2, which is NOT the same equation.( OR is it?, can I just use that?)

For my situational problem, there is a part where the 2 liquids leak(quantified) and mix together in a room to produce the gas. I need these basic understandings above to be able to deduce the ppm of H2S.

What I plan on doing is: (Ultimate goal : Find ppm of leaked gas within the volume in air)

1. Using a balanced equation(This is where I am stuck, because I don't know how to work with CaSx), determine the amount of H2S in moles.
2. ??? How would I find the ppm, I am allowed to use other information such as density.

The concentrations and amounts are: Hcl= 3.6L of 35% in water, and CaSx-calcium polysulfides 20% in water)

Title: Re: CaSx - What is this and how do I use it?
Post by: Arkcon on August 16, 2012, 08:59:49 PM
The x in this case is an unknown, just like in algebra.  We don't actually, and can't report, how much sulfur there is relative to the calcium.  So you won't find the answers in a reference.  However, for any given sample, you can use the moles of other reactants and products to come up with the ffective, local value for x.  This is what your teacher likely wants you to find out.
Title: Re: CaSx - What is this and how do I use it?
Post by: iLoveScience_103 on August 17, 2012, 12:03:00 AM
Would yOu please show me how to in this case? I've never dealt with variables in chemical equations like these and an example would help. Or atleast could you tell me how?

Because I understand what you mean a little bit but not fully.

Thank you, more replies would be appreciated!
Title: Re: CaSx - What is this and how do I use it?
Post by: Hunter2 on August 17, 2012, 12:54:12 AM
For CaSx you can say is CaS + (x-1)S

Develop a equation with calcium sulfide.
Title: Re: CaSx - What is this and how do I use it?
Post by: Borek on August 17, 2012, 03:16:55 AM
Balanced equation means you have the same number of atoms of all elements (and the same charge) on both sides of the reaction equation. That means for example for the reaction

aH2 + bO2 :rarrow: cH2O

if the reaction is balanced number of oxygen atoms on both sides is identical, or 2b=c, and number of hydrogen atoms on both sides is identical, or 2a=2c.

In the case of unknown stoichiometry of the compound you can still write similar equations. Iron(II) oxide is often non-stoichiometric, with exact composition around Fe0.95O. If you dissolve it in a hydrochloric acid, you can write the reaction equation as

FexO + 2xHCl :rarrow: xFeCl2 + xH2O + (1-x)/2O2

Now you can do stoichiometric calculations as usual.

Note: I am cheating a little bit, as FeO is non stoichiometric because it often contains some Fe(III) ions, so the reaction should look slightly different - but I am trying to show you the idea, not the exact chemistry.