How to calculate weight needed for a concentration

In summary, the conversation discusses the calculation for achieving a 5 uMol concentration of resveratrol in dimethylsulfoxide solution. The conversation covers the definition of molar concentration and the use of a calculator to determine the amount of resveratrol needed. The conversation also mentions the importance of understanding the density and safety considerations when working with dimethylsulfoxide.
  • #1
pyroartist
50
6
Please post this type of questions in HW section using the template and showing your work.
I haven't had a chemistry class in many years. Recently I saw an interesting article that used a solution of resveratrol (228.25 grams per mole) in dimethylsulfoxide (78.13 grams per mole). The concentration was listed as 5 uMol.
If I had 10 grams of DMSO how much resveratrol would I add to achieve the 5 uMol concentration? And how is this calculated? Thanks.
 
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  • #2
Start with the definition of molar concentration.
 
  • #3
Would you be clearer about the "5 uMoL" ? What is that unit? Micro-something. Either you mean, MOLES, MICROMOLES, MICROMOLES-or-LITER, MICROMOLES PER LITER,... What?
 
  • #5
Borek said:
M usually stands for mol/L, mM and μM are rather common and unambiguous extensions. What is a bit confusing is your way of calling it μMol.
Okay, micromoles per liter.
You want 5 micromoles per liter of resveratrol. You 'have' 10 GRAMS of DMSO and you wish to find how much resveratrol is needed.

Use x grams of resveratrol,
d is density of dimethylsulfoxide as grams per milliliter , which you need to look-up,
and you should fill in the unstated units of measure to be sure you see the way the two numbers work,
and the right side is as MOLES per LITER:
(x(1/228.25))/(10*(1/d)*(1/1000))=0.000005

(Micro moles per liter, the same as the number shown on the right side)
That is in plain text but you could rewrite in normal notation on paper, yourself so more understandable.
Solve for x.

Note: the density of DMSO is NOT 78.13 grams per mole and not moles per liter. See a handbook.

Also, note, https://en.wikipedia.org/wiki/Resveratrol
 
Last edited:
  • #6
I'd guess that a person should not go playing with dimethylsulfoxide without care and knowledge. Storage? Exposure? Grades of quality? Material Safety Data Sheet?
 
  • #7
https://en.wikipedia.org/wiki/Dimethyl_sulfoxide
According to Wiki, the density is almost like water at 1.1004 g cm−3.
78.13 is the molar mass, which I thought might have been needed.
Thanks for the formula. I will rearrange it on paper when I get a chance.
Also good to know was that uM means micro-moles per liter. Would not have guessed that.
 

1. How do I calculate the weight needed for a specific concentration?

In order to calculate the weight needed for a specific concentration, you will need to know the desired concentration and the molecular weight of the substance. The formula for calculating weight needed for a concentration is: weight (g) = concentration (mol/L) x volume (L) x molecular weight (g/mol).

2. Can I use any units for concentration and volume in the calculation?

It is important to use consistent units for concentration and volume in the calculation. For example, if the concentration is given in molarity (mol/L), then the volume should be in liters (L). If the concentration is given in mass per volume (g/L), then the volume should be in liters (L) as well.

3. How do I find the molecular weight of a substance?

The molecular weight of a substance can be found by adding up the atomic weights of all the elements present in the molecule. This information can usually be found on the chemical label or by searching online. There are also molecular weight calculators available online that can help with this process.

4. What if I need to make a certain volume of solution, but the concentration is not given in the desired units?

If the concentration is not given in the desired units, you can use unit conversion to convert it to the necessary units. For example, if the concentration is given in millimoles per liter (mM), but you need it in moles per liter (mol/L), you can multiply by 0.001 to convert from millimoles to moles.

5. Is there a specific order in which the values should be plugged into the formula?

Yes, the formula for calculating weight needed for a concentration should be followed in a specific order: first, multiply the concentration by the volume, and then multiply that result by the molecular weight to get the final weight value. This ensures that the units are correctly cancelled out and the resulting weight is in the correct units.

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