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aquablue8
Feb27-11, 09:32 AM
1. The problem statement, all variables and given/known data

What is the theoretical yield of calcium carbonate if 2.07 grams of calcium chloride dihydrate reacts with excess sodium carbonate according to the balanced chemical reaction shown below?

2. Relevant equations

Please use molar mass values calculated and rounded to the hundreths place, and round your answer to the hundredths place.

CaCl2•2H2O(aq)+Na2CO3(aq)→CaCO3(aq)+2NaCl(aq)+2H2O (l)

3. The attempt at a solution

I got the molar mass of CaCl2, which is 110.98, then I divided it by 2.07 g of CaCl2 which is the actual?? Am I way off track? That got me 229.73g CaCl2???
Borek
Feb27-11, 10:27 AM
I got the molar mass of CaCl2, which is 110.98, then I divided it by 2.07 g of CaCl2 which is the actual?? Am I way off track? That got me 229.73g CaCl2???

While calculating molar mass you ignored fact that you deal with dihydrate, and your answer refers to calcium chloride, while question asks about carbonate. I guess the latter is just a typo.
aquablue8
Feb27-11, 10:32 AM
I do not understand what you mean. Where did I go wrong in lay-woman's terms? lol!
Borek
Feb27-11, 10:35 AM
On the second read I see you confused much more than I saw earlier.

Let's start from the very beginning. What does it mean "dihydrate"?
aquablue8
Feb27-11, 10:35 AM
Two hydrations?
Borek
Feb27-11, 11:01 AM
Oops. What is hydrate?
aquablue8
Feb27-11, 11:02 AM
To add 2 hydrogen bonds by dehydration synthesis?
Borek
Feb27-11, 11:06 AM
No.

http://en.wikipedia.org/wiki/Hydrate
aquablue8
Feb27-11, 11:07 AM
Umm, I am really lost now!
aquablue8
Feb27-11, 11:10 AM
Okay, so two hydrogen bonds hydrated the solution???????
aquablue8
Feb27-11, 11:35 AM
Here is what I have attempted: 2.07gCaCl2 x 1 mol Ca/40.08g Ca x 2 mol Cl/2 mol Ca x 70.9g Cl2/ 1 mol Cl2 = 3.62 g CaCl2
Borek
Feb27-11, 03:19 PM
No.

Hydrate means when substance crystallizes it crystallizes with water, and there is a stoichiometric ratio of water to the substance. In this particular case you are told it is dihydrate, which means its formula is CaCl2.2H2O - you have even written it this way (correctly) in your first post. That means you need to accommodate for the water presence when calculating molar mass of the substance.

Here is what I have attempted: 2.07gCaCl2 x 1 mol Ca/40.08g Ca x 2 mol Cl/2 mol Ca x 70.9g Cl2/ 1 mol Cl2 = 3.62 g CaCl2

As explained at CF - 2 does not equal 3.
aquablue8
Feb27-11, 08:15 PM
Thank you for your help!