Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Boxxxed on October 02, 2010, 06:12:01 PM

Title: Stoichiometry Question
Post by: Boxxxed on October 02, 2010, 06:12:01 PM
Element X reacts with chlorine to give a chloride salt. It was found that 0.746 mol of element X combines with 79.8 g of chlorine gas (Cl2), to yield 131.8 g of chloride salt.


Determine the chemical formula of the chloride salt (show your steps).

Write a balanced chemical reaction for the above.
--------------

I've done some calculations and found out that Ga is element X.

How do I figure out how Ga+Cl2 react?
Title: Re: Stoichiometry Question
Post by: ooosh on October 02, 2010, 10:19:22 PM
Yes,the Relative atomic mass of element x is 69.7 ,and it's Ga,and the chloride salt is GaCl3,like AlCl3.
Title: Re: Stoichiometry Question
Post by: Boxxxed on October 03, 2010, 11:29:31 AM
Why is it GaCl3 and not GaCl or GaCl2 etc?
Title: Re: Stoichiometry Question
Post by: Boxxxed on October 03, 2010, 11:33:46 AM
Also 0.746 mol of Ga combines with 1.31 mole Cl2 to make 0.749 moles GaCl3. How can a balanced formula be derived from this?
Title: Re: Stoichiometry Question
Post by: Borek on October 03, 2010, 11:49:08 AM
What is molar ratio of elements in the compound?
Title: Re: Stoichiometry Question
Post by: Boxxxed on October 03, 2010, 12:10:37 PM
Molar ratio is 3:1 but I can't know that until I figured out what the compound is.
Title: Re: Stoichiometry Question
Post by: Borek on October 03, 2010, 01:45:58 PM
Yes you can. You know number of moles of element and from the other data you can calculate number of moles of chlorine.
Title: Re: Stoichiometry Question
Post by: Boxxxed on October 03, 2010, 02:57:14 PM
0.746 mole Ga

1.31 mol Cl2 = 2.62 mol Cl

2.62/0.746 = 3.5 moles Cl per mole Ga

=3.5 ratio? is this where the 1 third comes from?
Title: Re: Stoichiometry Question
Post by: Borek on October 03, 2010, 03:19:58 PM
Why 1.31 moles of Cl2?
Title: Re: Stoichiometry Question
Post by: Boxxxed on October 03, 2010, 03:48:03 PM
0.746 mol of element X combines with 79.8 g of chlorine gas

moles Cl2 = 79.8/70.9=1.13 moles

I see where I went wrong. So that's where the 1 third comes from I assume

Also 0.746 mol of Ga combines with 1.13 mole Cl2 to make 0.749 moles GaCl3. How can a balanced formula be derived from this?

So is the formula then Ga+3Cl----->GaCl3?

Or 2Ga+3Cl2--------->2GaCl3?
Title: Re: Stoichiometry Question
Post by: Borek on October 03, 2010, 04:07:30 PM
Quote from: Boxxxed on October 03, 2010, 03:48:03 PM
So is the formula then Ga+3Cl----->GaCl3?

Or 2Ga+3Cl2--------->2GaCl3?

These are not formulas, these are reaction equations.

The latter is the correct one, chlorine is always diatomic.