# Calculating concentration - (Aug/03/2014 )

Hi

Could any one help with this query. I would like to calculate the concentration that I used from a pure chemical Methyl laurate. The purity is 98%. MW is 214.34. I took directly 200, 100 and 50 microlitres for my experiment. Just wondering, how do I express this in concentration? such as in Molarity or in Micrograms/ml

what is the density of the compound (required to determine mass and moles of compound added) ?

final volume (required to determine concentration)?

Thank you. The density is 0.87 g/mL. The final volume I took for my experiment is 200, 100 and 50 microlitres (directly from the pure synthetic bottle for my experiment). However, I need to write it as final concentration, not as volume.

Is this correct way I am doing: 0.87g/ml = 870g/L = 870*98/100 = 852.6 g = 852.6/214.34 = 3.97 mol/L. So in 100 microlitres it is 0.397 and in 50 microlitres it is 0.19 M? Am I right? Thank you

I think this is correct up to your 3.97 mol/L result. I can make no sense of the next statement. The molarity of any amount of your chemical is unchanged. If you mix that amount into a larger volume, the molarity of the final solution will change, but to know the new molarity, you need to know the amount of volume you are diluting into.

I can't even figure out how you got the .397 M result.

reading your posts it seems you simple took 200 microliter , 100microliter and 50 microliter from the solution and thats it.

You need to tell in how much you diluted it? Was the end volume 200 microliter each time?

Thank you. phage434 and Pito. I simply took 200, 100 and 50 microlitres and used directly for my experiment (3 different volumes of same pure compound, but I would like to express as concentration). I did not diluted it. Coming to my calculation if it is 3.97 mol/L, then can it be a 0.397 M in 100 microlitres? I am not sure, if I calculated it right. I calculated based on : 3.97 mol in 1 Litre. So 1 litre = 1000 ml. So in 100microlitres it is 0.0397 M . Am I right now?

Thank you. phage434 and Pito. I simply took 200, 100 and 50 microlitres and used directly for my experiment (3 different volumes of same pure compound, but I would like to express as concentration). I did not diluted it. Coming to my calculation if it is 3.97 mol/L, then can it be a 0.397 M in 100 microlitres? I am not sure, if I calculated it right. I calculated based on : 3.97 mol in 1 Litre. So 1 litre = 1000 ml. So in 100microlitres it is 0.0397 M . Am I right now?

But the concentration is the same than!

If you did not dilute it you would just have added the same concentration to your sample...

The sample itself of course would have an effect on the end concentration.

I will give you a simple example:

if you have 10 moles per liter for a certain solution than this concentration does not change whether you have taken 100 microliter or 50 microliter.

The concentration is the same!

The amount of moles is different of course: for 100 microliter you have twice the amount as for 50 microliter.

1 liter = 10 moles

100 microliter = 0,1 ml = 0,1ml x 10^-3 liter , this meaning 10/10 000 moles!

50 microliter is than the half of 10/10 000 moles..

Now the end concentration of course depends on to what you add this 100 microliter or 50 microliter.

Thank you. phage434 and Pito. I simply took 200, 100 and 50 microlitres and used directly for my experiment (3 different volumes of same pure compound, but I would like to express as concentration). I did not diluted it. Coming to my calculation if it is 3.97 mol/L, then can it be a 0.397 M in 100 microlitres? I am not sure, if I calculated it right. I calculated based on : 3.97 mol in 1 Litre. So 1 litre = 1000 ml. So in 100microlitres it is 0.0397 M . Am I right now?

But the concentration is the same than!

If you did not dilute it you would just have added the same concentration to your sample...

The sample itself of course would have an effect on the end concentration.

I will give you a simple example:

if you have 10 moles per liter for a certain solution than this concentration does not change whether you have taken 100 microliter or 50 microliter.

The concentration is the same!

The amount of moles is different of course: for 100 microliter you have twice the amount as for 50 microliter.

1 liter = 10 moles

100 microliter = 0,1 ml = 0,1ml x 10^-3 liter , this meaning 10/10 000 moles!

50 microliter is than the half of 10/10 000 moles..

Now the end concentration of course depends on to what you add this 100 microliter or 50 microliter.

Thank you. The result of my experiment is like this, as the volume increases from 50 to 200, the results were better. I did not get good results when I used 50 microlitre. Does this mean concentration has an effect on my sample? So you are saying, even though the volume increases, concentration remain same? Am I right? Do I need say as the volume increases the results were better, (instead of saying as concentration increases the results were better)?

But the concentration is the same than!

If you did not dilute it you would just have added the same concentration to your sample...

The sample itself of course would have an effect on the end concentration.

I will give you a simple example:

if you have 10 moles per liter for a certain solution than this concentration does not change whether you have taken 100 microliter or 50 microliter.

The concentration is the same!

The amount of moles is different of course: for 100 microliter you have twice the amount as for 50 microliter.

1 liter = 10 moles

100 microliter = 0,1 ml = 0,1ml x 10^-3 liter , this meaning 10/10 000 moles!

50 microliter is than the half of 10/10 000 moles..

Now the end concentration of course depends on to what you add this 100 microliter or 50 microliter.

Thank you. The result of my experiment is like this, as the volume increases from 50 to 200, the results were better. I did not get good results when I used 50 microlitre. Does this mean concentration has an effect on my sample? So you are saying, even though the volume increases, concentration remain same? Am I right? Do I need say as the volume increases the results were better, (instead of saying as concentration increases the results were better)?

But what did you do with the "volumes" ?

Did you add the 200 microliter to something else?

The concentration stays the same! In the 200 microliter , 50 microliter and 100 microliter the concentration is the same!

The total amount of your substance is different of course..... because 200 microliter has more moles in it than 50 microliter!

But the concentration is the same than!

If you did not dilute it you would just have added the same concentration to your sample...

The sample itself of course would have an effect on the end concentration.

I will give you a simple example:

The concentration is the same!

1 liter = 10 moles

100 microliter = 0,1 ml = 0,1ml x 10^-3 liter , this meaning 10/10 000 moles!

50 microliter is than the half of 10/10 000 moles..

Now the end concentration of course depends on to what you add this 100 microliter or 50 microliter.

Thank you. The result of my experiment is like this, as the volume increases from 50 to 200, the results were better. I did not get good results when I used 50 microlitre. Does this mean concentration has an effect on my sample? So you are saying, even though the volume increases, concentration remain same? Am I right? Do I need say as the volume increases the results were better, (instead of saying as concentration increases the results were better)?

But what did you do with the "volumes" ?

Did you add the 200 microliter to something else?

The concentration stays the same! In the 200 microliter , 50 microliter and 100 microliter the concentration is the same!

The total amount of your substance is different of course..... because 200 microliter has more moles in it than 50 microliter!

Sorry I am totally confused with the term concentration and amount. I did not diluted 200 microlitres. I know, you understood my point. But I am confused. I am working on fungal inhibition with a pure chemical compounds described above. I took 3 volumes and tested on fungal inhibition. When I used 200 microlitre the inhibition was higher, but could not see inhibition at 50 microlitre. So If I understood correctly, I used only one concentration (is conc expressed in %?) or (I think concentration is expressed in moles, millimoles, micromoles - if I dilute from 1 mole to 1milli mole, the concentration usually decreases because of dilution?). So in my experiment, is the quantity/amount or concentration (do not know the right term here to be used) have an effect on fungal growth. Also in one paper, authors used 1 ng 1 μg 1 mg. They also found good results at higher 1 mg. But they said concentration? Is this right term or do they have say quantity/amount.

If you are saying 200 microliters has more moles than in 50 microlitre (Is this not a concentration?). Then in my calculation described above 3.97 mol in 1 Litre. So 1 litre = 1000 ml. So in 100microlitres it is 0.0397 M . So 100 microlitres has less moles?

Thank you and Sorry