# Can anyone help me with my chem homework?

Discussion in 'Off Topic [BG]' started by Kibuddy, Nov 12, 2006.

1. ### Kibuddy

Apr 30, 2005
Alright all of you chem buffs. Here's a question for you.

I have a 100mL solution of SrCl[SUB]2[/SUB]*6H[SUB]2[/SUB]O. To make the solution, we took 4.76g of the hydrate and added enough water to dissolve the powder and create the 100mL solution. Now I need to calculate the molarity.

I wound up with a molarity of .179M, but I'm not sure I did it correctly. Can anyone double check my work for me?

Here's my work to the best of my typing ability (it's supposed to be dimensional analysis):

4.76g | 1mol | 1000mL|

100mL | 266.64g | 1L |

= .179M

2. ### Mike MoneyIn Memoriam

Mar 18, 2003
Bakersfield California
Avatar Speakers Endorsing Hooligan
Sure.

Why not.

Dude, honestly, Chemistry class is one of those classes that on the last day of school, when you leave that class for the last time... you don't remember ANY OF IT.

3. ### Kibuddy

Apr 30, 2005

Well, let's just say that I enjoy the class and am considering going to college to major in chemistry. So, it may not have been worthwhile for you, but it sure as hell is to me.

4. ### Sonic_Death

Jan 12, 2005
Wantagh, New York

5. ### Christopher

Apr 28, 2000
New York, NY
It's been a really long time since I did this, so take it with a grain of salt, but the atomic mass of the hydrate should be around 267 by my count, so a mole of the stuff should be 267 g. You have 4.76 g of the stuff, which works out to 0.0179moles in 100 mL, or 0.179 moles in 1L.

Looks right to me.

6. ### AmazingGracePlayer

Oct 8, 2006
Summit, NJ
I can't believe, I took AP chem last year and I don't even remember how to do this kind of problems! Ugh1!!

7. ### Kibuddy

Apr 30, 2005

Awesome, thanks a bunch!

8. ### SomecallmeTim

Ain't that the truth? I took multiple chemistry classes in high school, but I remember next to nothing about them.

9. ### vindy500

bah chemistry

10. ### Kibuddy

Apr 30, 2005
Here's another one:

We reacted sodium carbonate and strontium chloride hexahydrate and got strontium carbonate as a product. Why is it safe to pour strontium carbonate down the sink?

I really have no idea. I would think it has something to do with it being neutralized, but I'm not sure. At all.

11. ### Demon

Mar 17, 2006
Sweden, Stockholm
Put black powder in, always works.

12. ### dlloydzzzzzzzzzzzzzzz

Apr 21, 2004
Scotland
Yep, that's right, but you'd be better off calling that 179 mM

Apr 21, 2004
Scotland

14. ### Kibuddy

Apr 30, 2005

Oh man. I feel like an idiot. :scowl:

Thanks for the help!

15. ### Kibuddy

Apr 30, 2005
Okay, this should be my last question:

I have 5.3g sodium carbonate and 4.76g strontium chloride hexahydrate and got 1.09g strontium carbonate (really bad yield, I'm aware).

How do I determine how much of the sodium carbonate was not used (the hydrate is the limiting reactant)? I vaguely remember something to do with ratios, but I can't remember how to do it. Could someone explain the process to me (and hopefully not give away the answer)?

16. ### Poop-LoopsInactive

Mar 3, 2006
Auburn, Washington
Don't you have a chem book or something? This stuff is pretty rudimentary. Limiting reactant I think is correct, but I also don't remember the exact process to find this stuff, so just check your book. It should have a detailed explanation.

17. ### Kibuddy

Apr 30, 2005

My book is in my locker scowl. And keep in mind I'm a first year chem student, so I'm still trying to get a grasp on this stuff.

18. ### Poop-LoopsInactive

Mar 3, 2006
Auburn, Washington
Read the book. It's that easy. Books will have explanations in them with examples. If then you cannot understand how to do a problem, ask away. But it just seems like you have no idea what you are doing, because you don't know the concept yet. This is the hardest part in learning something, but that's why it's the most important, too.

If you don't have the book with you (shame on you! ) then Google is your friend.

http://www.chem.tamu.edu/class/majors/tutorialnotefiles/limiting.htm
http://wine1.sb.fsu.edu/chm1045/notes/Stoich/Limiting/Stoich07.htm

19. ### Kibuddy

Apr 30, 2005

Here's the thing: it's not that I don't understand stoichiometry. I can do basic stoichiometric equations with ease. This question just flipped things around in a direction that I've never seen before. The only stoich I've been doing so far is theoretical yield, actual yield, molarity, etc. I've not yet been shown how to determine how much of a certain reactant was actually used. Maybe it was just a case of not knowing how to apply it yet. I don't know. All I know is that this was a new scenario for me, and I didn't know how to go about solving it.

So, maybe it is a very rudimentary concept for you, and if it annoys you that I asked, then I am sorry. But I AM a first year student. These are all brand new concepts to me. I've never even seen this particular problem at hand until now.

And I take some offense to your accusation that I don't know what I'm doing. It was a simple question about an application I had not seen. That doesn't mean that I don't know anything about stoichiometry. I'll stop here, though, as I'm starting to get all defensive, and nobody likes a defensive, angsty teen.

And thank you for the links. They've been very helpful to me.

20. ### steve21Inactive

I'm in AP Chem and I don't know this.