Chemistry Help.

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".

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.

2.99 g?

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.

Edited by Uncle Rudder - 17 October 2007 at 11:01pm

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.

jerseypaint wrote: 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.

Haha to this day I still don't completely understand what a "mole" is.

I'm assuming this is a chem course at the high school level?

Jack Carver wrote: 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.

I want a mol of grapefruit. My mol would have the mass of the earth.

I'll settle for a mol of pennies

So I guess this is what I have to look forward to after the next few chapters of my Chem class...