Chemistry Help.
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Topic: Chemistry Help.
Posted By: Hysteria
Subject: Chemistry Help.
Date Posted: 17 October 2007 at 10:30pm
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As a prelude, I feel the need to mention that my teacher is horrible.
Rather than teach like a normal teacher, he simply reads power point
presentatiosn to us. He even recognizes that he is horrible which is
why he allows us to take home our tests after we sit there struggling
for an hour and fifteen minutes. Anyway, here is the problem I am
having trouble with: "If one mixes 150.0 milliliters of a .204 Molar CuSO4 solution with 150.0 milliliters of a 1.50 Molar NaOH solution, how many grams of solid copper(II) hydroxide Cu(OH)2 precipitate will form? Assume reaction goes 100% completion and don't forget significant figures!" If I guess right, this should be a Gravimetric Analysis problem, but even with the book in front of me, I can not figure it out. In before "Do your own homework, n00b". |
Replies:
Posted By: ANARCHY_SCOUT
Date Posted: 17 October 2007 at 10:37pm
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42.
------------- Gamertag: Kataklysm999 
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Posted By: Jack Carver
Date Posted: 17 October 2007 at 10:49pm
| I don't remember what a "gravimetric analysis" problem is, but find out how many moles of Cu and OH will go into solution. See which will be the limiting reactant, then find out how many moles of Cu(OH)2 you can make. Then switch moles to grams with the atomic weights. |
Posted By: Uncle Rudder
Date Posted: 17 October 2007 at 10:49pm
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convert mililiters to liters, multiple by the molarity for both reagents find the limiting reactant, it would be helpful to write out a balanced chemical reaction this the limiting reagent number of moles and the stoic ratio to find the moles of product. convert these moles to grams through the molecualr weight.
Hope thats more helpful than just an answer. ------------- 
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Posted By: obnoxious
Date Posted: 17 October 2007 at 10:52pm
| 2.99 g? |
Posted By: ¤ Råp¡Ð F¡rè ¤
Date Posted: 17 October 2007 at 10:53pm
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Thank God I'm done with chem. I remember those problems. Unfortunately, I've forgotten how to do them. What Uncle Rudder said sounds correct though.
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Posted By: Uncle Rudder
Date Posted: 17 October 2007 at 10:53pm
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I got an answer of 2.98 grams assuming I didn't make any stupid mistakes, I did it in a bit of a hurry.
Edit: For a problem like this you can let the units guide you through it. Molar is molarity, which is moles of solute per liter solution, and you were given a volume so mol/L (L) cancells liters out leaving you with moles, and then from here its a basic stoic problem. And after you have done your stoic mole ratios use the units of the molar mass (g/mol) to get you to grams mol * (grams/mol) = grams
I don't know if your teacher showed you this method of problem analysis but it works wonders when it comes to conversions and starting problems.
I feel your pain, my physics prof is the same way. He reads his slides and never really shows how the equations are applied to problems...and I'm pretty sure my book was written to delibetly confuse people. sorry for the poor typing. Ironically enough I'm doing my own chemistry lab report right now. -------------
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Posted By: Hysteria
Date Posted: 17 October 2007 at 11:26pm
| Awesome, thanks for all the help, guys. |
Posted By: jerseypaint
Date Posted: 17 October 2007 at 11:38pm
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God, I hated Chem, and I only had it at the highschool level. I especially hated the whole moles, molarity and other things. Way too many equations to remember. ------------- 
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Posted By: Ticalxx421
Date Posted: 17 October 2007 at 11:44pm
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WoW. I just relized how bad my school system really was. ------------- [IMG]http://i14.tinypic.com/73e0l8j.jpg"> Represent! |
Posted By: ¤ Råp¡Ð F¡rè ¤
Date Posted: 18 October 2007 at 12:38am
Haha to this day I still don't completely understand what a "mole" is. -------------
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jerseypaint wrote:Posted By: Shub
Date Posted: 18 October 2007 at 12:48am
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A mole is a unit of measurement.
Every element of the periodic table has an atomic weight. For instance, if you take nitrogen (N), it has an atomic weight of 14. If you had 14 grams of nitrogen in a beaker, you would have 6.02x10^23 (Avagadro's Number) atoms in the beaker. |
Posted By: Uncle Rudder
Date Posted: 18 October 2007 at 2:52pm
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I'm assuming this is a chem course at the high school level? -------------
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Posted By: Jack Carver
Date Posted: 18 October 2007 at 2:57pm
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A mol is the same thing as a dozen, only a whole lot more. A dozen apples is 12 apples. A mol of apples is 6.022 X 10^23 apples. A mol of carbon-12 atoms is 6.022 X 10^23 atoms and happens to weight exactly 12 grams. |
Posted By: reifidom
Date Posted: 18 October 2007 at 3:00pm
I want a mol of grapefruit. My mol would have the mass of the earth. ------------- 
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Posted By: Jack Carver
Date Posted: 18 October 2007 at 3:04pm
| Well I don't have a mol, but here's http://http://www.youtube.com/watch?v=llCJg5LiKo8 - 10,000 watermelons ! |
Posted By: Uncle Rudder
Date Posted: 18 October 2007 at 3:37pm
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I'll settle for a mol of pennies -------------
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Posted By: Pezzer
Date Posted: 18 October 2007 at 5:37pm
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I honestly have absolutely no idea. I don't use chemistry daily like I do other sciences, so I forgot most of it.
------------- Suck, sqeeze, bang, blow, and GO! 
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Posted By: MeanMan
Date Posted: 18 October 2007 at 9:15pm
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So I guess this is what I have to look forward to after the next few chapters of my Chem class... ------------- 
hybrid-sniper~"To be honest, if I see a player still using an Impulse I'm going to question their motives." |
Posted By: Hysteria
Date Posted: 19 October 2007 at 3:18am
It is a college course. It is titled "Principles of Chemistry I". |