# Concentration from density and purity

• Hallucinogen
In summary, the individual is trying to create a 1.5 x 10^-4 M solution of monothioglycerol from a stock solution with a concentration of 1.25 g/mL and a molar mass of 108.16. They have determined that a 10-fold dilution is needed, which would result in a molarity of 1.15 M. However, after calculating the amount needed for a 100 mL solution, they are unsure if they have used the density correctly. Their final calculation suggests that they would need 13 microlitres of the stock solution to achieve the desired concentration.
Hallucinogen

## Homework Statement

This isn't homework, rather it's regular work. I have a >97% solution of 1-thioglycerol, the density of which is 1.25 g/mL. I am trying to get a 1.5 x 10-4 M solution at the end, and I suspect the instructions I have been given are incorrect.
Molar mass = 108.16

## Homework Equations

Concentration = Density / molar mass.

## The Attempt at a Solution

The molarity of my stock solution is (1.25 * 1000) = 1250 g/L. 1250 / 108.16 = 11.5 M.
I am instructed to make a 10-fold dilution, giving me a molarity of 1.15 M.
I should then take 6.5 microlitres and add this to a final volume of 100 millilitres.
But 1.15 x (6.5 x 10^-6) = 7.5 x 10^-6. Divided by (100 x 10^-3) = 7.5 x 10^-5 M, which is half the concentration I need?

Are you looking for a solution that is 1.5 x 10-4 M in hydroxyl groups (2 per molecule)?
Otherwise I agree with your calculation.

No, I'm looking for 1.5 x 10-4 M monothioglycerol.

I calculated this again from the end concentration, and would just like anyone to proof-check it.
If we start with the concentration I want at the end (1.5 x 10^-4 moles per litre), and if I want this in a volume of 100 millitlitres:
(1.5 x 10^-4) x (0.1) = 1.5 x 10^-5 moles.
Multiply the moles needed by the molecular mass to obtain the grams needed: (1.5 x 10^-5) x 108.16 = 0.00162 grams.
The density is 1.25 grams per millilitre, but we need the grams per litre amount, so 1.25 x 1000 = 1250 grams per litre.
Divide the grams by the density in grams per litre to obtain the volume needed: 0.00162 / 1250 = 1.3 x 10^-6 L.
This is 1.3 microlitres. Therefore, if I makea 10-fold dilution of my stock solution, I should need 13 microlitres per 100 millilitres of media to make.
This is the same answer as I got in my original post, but I'm uncertain if I've used the density correctly...

## What is concentration from density and purity?

Concentration from density and purity is a method used to determine the amount of a substance in a solution by measuring its density and purity.

## How is concentration from density and purity calculated?

The concentration is calculated by dividing the mass of the substance by the volume of the solution. This is then multiplied by the purity percentage of the substance.

## What is the purpose of determining concentration from density and purity?

Determining concentration from density and purity is important in many scientific fields, such as chemistry, environmental science, and pharmaceuticals. It allows researchers to accurately measure the amount of a substance in a solution, which is crucial for experiments and quality control.

## What tools are needed for measuring concentration from density and purity?

To measure concentration from density and purity, you will need a balance or scale to measure the mass of the substance, a graduated cylinder or other volumetric tool to measure the volume of the solution, and a purity percentage determined through testing or provided by the manufacturer.

## Are there any limitations to using concentration from density and purity?

Yes, there are some limitations to this method. It assumes that the substance is uniformly distributed throughout the solution and that the purity percentage is accurate. Additionally, this method may not be suitable for substances that have a large range of purity percentages or when the substance is not completely dissolved in the solution.

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