BF2S Forums need help with a chem question

I believe the density is g/cm cubed.

You have to account for the differences of temperature and pressure from STP

HurricaИe wrote:

Aspirin, C9H8O4, is produced through the reaction of salicylic acid (C7H6O3) and acetic anhydride (C4H6O3):

C7H6O3 + C4H6O3 ---> C9H8O4 + HC2H3O2

The equation is balanced, and this is the question I'm stuck on

At 20 degrees Celsius, how many liters of acetic acid, HC2H3O2, would be formed? The density of HC2H3O2 is 1.05 g/cm³

I have no idea how to do that. This is on the chapter about Stoichiometry, and I have no idea what temperature and density have to do with this.

There has to be more to the question than this? Like how many moles of one of the reactants were used or the mass of aspirin produced or something :S

[CSE]Anubis wrote:

Do you have any volumes given to you?

no

HurricaИe wrote:

[CSE]Anubis wrote:

Do you have any volumes given to you?

no

I was thinking along the lines of mass = density x volume but as your given no volumes I'm stumped.  Sorry.

Edit: I got confused with the question so what I said doesn't make much sense.

Last edited by [CSE]Anubis (2008-02-27 15:10:13)

Shem wrote:

HurricaИe wrote:

Flaming_Maniac wrote:

I believe the density is g/cm cubed.

You have to account for the differences of temperature and pressure from STP

ja it's cubed

And my head exploded when you said that second sentences. For example, here's another question for that same formula

What mass of aspiring in kg could be produced from 75.0 mol of salicylic acid?

I was able to do that fine w/ stoich, but then they throw this question out of fucking nowhere

This one is quite easy.

1 mol of aspirin is produced from 1 mol of saly, therefore 75 mols of aspirin are formed.

Aspirin = 180gmol

180 x 75 = 13500g

13500/1000 = 13.5kg.

That looks right?

EDIT:

Ok worked the other one out as well, give me a minute to write it down.

I worked it out at 4.725dm3

Ja the 75 mol one was right, but how did you get the one in the OP (the liter one)?

Like I said, let's just wait for S.Lythberg.

On further thought, if this reaction is not an equilibrium temperature should nto have any major factor in the amount of mols produced at the end, only the speed at which the reactants are produced?

Or have I completely forgotten something big out?

Flaming_Maniac wrote:

Where are you getting these masses man?

Relative Molecular Masses.

for example, 1mol of O2 will weigh 32g.

Last edited by Shem (2008-02-27 15:26:58)

Just say that when you mix Aspirin with your stomach acid, you will asplode.

Shem wrote:

On further thought, if this reaction is not an equilibrium temperature should nto have any major factor in the amount of mols produced at the end, only the speed at which the reactants are produced?

Or have I completely forgotten something big out?

Flaming_Maniac wrote:

Where are you getting these masses man?

Relative Molecular Masses.

for example, 1mol of O2 will weigh 32g.

Psh innaccurate, we had to go to at least two decimal places.

Since you aren't dealing with gases they must have put that temp in to throw you. I suppose work it out as usual.

HurricaИe wrote:

Ryan wrote:

Just say that when you mix Aspirin with your stomach acid, you will asplode.

lol

my answers sheet says "4.29L HC2H3O2" but that's no help since I still need to show my work.

Well theres your answer, I did it.

I noticed a little mistake, I've already edited it, look back up at my post, all the working is there mate.

EDIT EDIT:

Ok, so again on the same principles, we are working on a 1 mol to 1 mol basis,, work out the Mr, which is 60

60 x 75mol = 4500g.

1.05gcm-3

so, essentially to to carry this amount, 4500/1.05 = 4285cm3

4285/1000 to convert to dm3, voila.

Incase you are feeling lazy.

It's actually pretty simple stuff, just have to work out unknowns with simple math.

Last edited by Shem (2008-02-27 15:36:34)

HurricaИe wrote:

"Chemistry I"

And ya, thanks for the answer But  I just don't get it.

edit: where the hell did 60 come from

Give me a few minutes ill explain my method.

HurricaИe wrote:

"Chemistry I"

And ya, thanks for the answer But  I just don't get it.

I'll explain best I can.

The unknown they have given us is the amount of solution formed at the end of the reaction, the formula gives us a piece of information we can use, that being the mol conversion.

For example, in the reaction

CH4 + 2O2 -> 2H2O + CO2 we have the following proportions:
  1    :   2   ->   2     :    1

this means we know how many mols will be produced at the end, we have an easy one, meaning there will be both 75mol of reactant and product.

From knowing this and knowing how many mols of one of the reactants we now need to work out the Mr, this is worked out by adding up the Relative Atomic Mass (Number above the Symbol on the periodic table) so in this case we have:

4 Hydrogens = 4

2 Carbons = 24

2 Oxygens = 32

Add them all up we have 60gmol (Grams per mol)

we will have 75 mols of this, as previously explained, so simply multiply this by 75 = 4500g

we know that the density of mols per cm3 = 1.05, so divide 4500 by 1.05 to work out the volume of the liquid = 4,285cm3 and divide that by 1000 to find out a dm3 (a litre) = 4.285.

I HOPE thats helped clear things up.