[cjp88]

Hello everyone, sadly I'm stuck on a question from my assignment booklet.  Normally I don't have a lot of problems in science, however chemistry is something I'm struggling on.  The book I'm reading doesn't give any examples for this problem.

While investigating mole ratios, a group of students collected data for the chemical reaction 2 NaOH(aq) + CaCl2(aq) -> 2 NaCl(aq) + Ca(OH)2(s).  The students wondered what would happen if an excess of NaOH was used.  Their teacher approved a procedure in which the solutions containing 3.00 g of NaOH and 2.10 g of CaCl2 were combined.  Based on the quantities of these reactants, what amount of Ca(OH)2(s) is produced?

I know how to do basic mole ratio's, just not with the added stuff.  I have no idea how 2 NaOH(aq) + CaCl2(aq) -> 2 NaCl(aq) + Ca(OH)2(s) would change with the added g's and how this works.

I under stand that the 2 in front of NaOH(aq) is the atoms used, but how do you use the g's added?  I'm so confused with this question.  I need to answer this question in a mol.

I'm not looking for anyone to give me the answer, and I really don't want the answer, I'm looking for help on understanding the question to obtain the answer.  Hopefully I can understand this stuff soon, thanks!

[enahs]

First, your chemical equation needs work.

You have two sodium atoms on the left side (reactants) but only one on the right side (products).
Does this make any sense?

[cjp88]

I'm sorry, I wrote the question out wrong.  It's supposed to be a 2 as well, sorry about that.

[Yggdrasil]

The molecular weight of a substance will tell you the relationship between grams and moles.  For example, sodium chloride (NaCl) has a molecular weight of 58.44 g/mol.  This means that one mole of NaCl has a mass of 58.44g.  The molecular weight can be found by adding the atomic weights of the atoms in the compound (e.g. NaCl = 22.99 + 35.45).

[cjp88]

Thanks for the response!   

So far I got NaCl to eqaul 58.44g and CaCl with 75.53g.  With the added amount they should be NaCl 119.88 g/mol (because two atoms and 3.00g) and CaCl 77.63 g/mol (because of the added 2.10g).

I'm hoping I got that all right, now I'm looking to find how much Ca(OH)2(s) was produced.  I'll post back with my results once I look over my book.  Sadly the examples in this book are not too helpful.

[enahs]

You are getting all mixed up.
The balanced chemical equation only relates molecules (or groups of molecules called mol's), not mass (grams)!


Check out this site, and read it and look at the examples.
http://dbhs.wvusd.k12.ca.us/webdocs/Stoichiometry/Stoichiometry.html

[cjp88]

Thanks for the link, I understand a bit better of where I went wrong but I'm confused. (Wish I had a better book).  I've read about half of that site which is helpful so far.  I'll read more in the morning, been up for over 16 hours attempting to understand chemistry.  If only I was as good with chemistry as I am with physics.

Thanks again everyone, any other help you can provide would be greatly appreciated!  I'll post back sometime tomorrow with my results.