[radonreds]

I'm creating an experiment. My professor says it has to be within a 100 mg scale. I need to figure out how much of everything to use. I'm reacting 1,3 diaminopropane(on a 100mg scale) with acetophenone with methanol(~15ml) as a solvent. The density of acetophenone is 1.028 and mw:120.15 Oh yeah: and its 1:2 if that helps
I totally forget the equation needed to figure this out. I would be so thankful if someone told me! or helped me work through this.

I think it has something to due with multiplying the density by .1, but my memory is foggy to say the least. And I don't want to start the experiment and just use totally the wrong amount.

Any help how be greatly appreciated!

[Borek]

Simple stoichiometry and conversion between moles, mass, volume and density, not clear to me what you are missing.

[radonreds]

Simple stoichiometry and conversion between moles, mass, volume and density, not clear to me what you are missing.

i know its simple. Im just fudging up the stoichiometry. terrible at it. so is this right 1.028 x 120.15 x .1 = 12.31g of acetophenone. And for 1,3 diaminopropane it would be .888 x 74.12(mw)x.1= 6.58g
and since it is a 1 to 2 I would use 12.31 g of acetophenone and 13.16 g of  1,3 diaminopropane

[Borek]

No idea what you are doing. To be honest, I don't understand like someone not understanding basic stoichiometry can be allowed to design an experiment of this type, this is a disaster waiting to happen 

Start with 100 mg of either reagent (hint: select the one with the higher molar mass), calculate number of moles, use molar ratio to calculate how many moles of the other reagent you need, convert moles of the other reagent to mass, convert both masses to volumes using densities.

[radonreds]

No idea what you are doing. To be honest, I don't understand like someone not understanding basic stoichiometry can be allowed to design an experiment of this type, this is a disaster waiting to happen 

Start with 100 mg of either reagent (hint: select the one with the higher molar mass), calculate number of moles, use molar ratio to calculate how many moles of the other reagent you need, convert moles of the other reagent to mass, convert both masses to volumes using densities.

I couldn't agree with you more! I tested into this program, so Im doing my best.
So let me just walk through the first step, please.

.1g x 1mol/120.15 = 8.32 x 10 -4 x 2 = 16 .64 x 10 -3 moles of 1,3 diamino

.1 /1.028  = .097g or 97.27 mg amount of Acetophenone

16 .64 x 10 -3 moles x (1g/ 74.12 mol) = 2.245 x 10^-4 g x (1ml / .888 g) =

= 2.52 x 10^-4 ml or .000252 ml amount of diamino

Ok where did I go wrong? because that looks totally wrong.



16 .64 x 10 -3 moles of 1,3 diamino x

[fledarmus]

I feel your pain. I'm guessing you had this a couple of years ago in basic chemistry classes, and now you're in undergraduate research and your professor tossed this at you as kind of a sink or swim?

If this is the first time you've done this in a while, write everything out explicitly and keep track of the units. Start by writing out your reaction, so you can account for all your stoichiometry. Then begin your calculations.

In your first calculation, you start by calculating the number of moles you would have with 100 mg of 1,3-diaminopropane. Why are you multiplying this by two?

In your second calculation, you start with... what? Certainly not 100 mg, or you wouldn't be trying to apply a density calculation.

Your third calculation, your units are off so you've got things on the wrong end of the fraction. When you're converting grams to moles, the molecular weight has the units grams/mole, not moles. (you write "74.12 mol")

Try again, with more attention to explicitly writing out the details. Let's take it from the ground up.

[radonreds]

Ok, thanks.


.1g divided by 120.15g/mol = 8.32 x 10 -4 x 2 (# of moles of Acetophenone), My professor gave us, it is a 1:2 ratio. So I assumed you would just x the # of moles of Acetophenone by two to get the # of moles of dianimo. 16.64 x 10-3 moles of dianimo multiply that 74.12g/mol = .112g of dianimo

if I use 1 gram of dianimo instead of Acetophenone:

.1g divided by 74.12g/mol = .00134mol (# of moles of dianimo), it is a 1:2 ratio. So I assumed you would just x the # of moles of dianimo by two to get the # of moles of Acetophenone. .0026 moles of acetophenone x 120.15g/mol =.315g of Acetophenone

one of my classmates helped me and he did it this way. .1g of DAP divided by the density of DAP (0.863g/mL) which gave him 0.11587mL. he then multiplied this by the density of acetophenone (1.028g/mL) giving me 0.119g needed which is equivalent to 0.991mmol; compared to 1.35mmol of DAP.

So confused and yes totally tossed in this class by my professor!

[Borek]

.1g divided by 120.15g/mol = 8.32 x 10 -4 x 2 (# of moles of Acetophenone), My professor gave us, it is a 1:2 ratio. So I assumed you would just x the # of moles of Acetophenone by two to get the # of moles of dianimo. 16.64 x 10-3 moles of dianimo multiply that 74.12g/mol = .112g of dianimo

if I use 1 gram of dianimo instead of Acetophenone:

.1g divided by 74.12g/mol = .00134mol (# of moles of dianimo), it is a 1:2 ratio. So I assumed you would just x the # of moles of dianimo by two to get the # of moles of Acetophenone. .0026 moles of acetophenone x 120.15g/mol =.315g of Acetophenone

Not bad, but there is a serious problem. In both cases you are multiplying by 2, even if in one case the ratio is 1:2 and in the other 2:1? (it must be reversed depending on which substance is the one you started calculations with).

one of my classmates helped me and he did it this way. .1g of DAP divided by the density of DAP (0.863g/mL) which gave him 0.11587mL. he then multiplied this by the density of acetophenone (1.028g/mL) giving me 0.119g needed which is equivalent to 0.991mmol; compared to 1.35mmol of DAP.

Wrong - substances don't react on the 1mL:1mL basis. They react in molar ratio. Your approach above is much closer.

totally tossed in this class by my professor!

Sorry, but I disagree. It is like starting calculus class and being surprised you are expected to know how much is 5 times 7.