Finding Mass of Solute: Equation & Experiment Ideas

[Sayuri09]

Homework Statement

I'm doing an experiment for Science Fair, and one of the parts requires that I know the mass of a solute (NaCl) dissolved in a solvent (water). Is there any equation I can use to find this? I cannot use concentration, but I have the total mass of the solution, the total volume of the solution, and the molar mass of the solute (NaCl). I can also calculate the total density of the solution, so let's add that, as well.

Homework Equations

For the solute:
Mass = Molarity x Molar Mass x Volume

The Attempt at a Solution

Using the equation above, I've tried to plug in different variables in the place of variables I didn't know up-front.

Mass = Molarity x Molar Mass x Volume
Mass = (Moles / Volume) x Molar Mass x Volume
Mass = ((Mass / Molar Mass) / Volume) x Molar Mass x Volume
Mass = ((Mass / Molar Mass) / (Mass / Density)) x Molar Mass x (Mass / Density)

Of course, simplifying all of this cancels Mass, what I was trying to find in the first place, which makes me wonder why I even did all of that substitution for nothing.

I'm thinking there's a different, better way to do this, probably a different equation. But, also, because I am doing this within an experiment, any hands-on method would work, too (just something feasible, please?).

Thanks in advance!

 

[Borek]

Basically you can't do anything without knowing more. You can use density tables to check out concentration.

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methods

 

[Blueshift5]

Hello,

Thank you for reaching out with your question. It's great to see that you are conducting an experiment for your Science Fair project! Finding the mass of a solute in a solution can be done using the equation you mentioned, but there are a few things to keep in mind.

Firstly, since you cannot use concentration, you can instead use the molarity of the solution. Molarity is defined as moles of solute per liter of solution. So in your equation, instead of using just "Molarity," you can use "(Moles of solute / Volume of solution)." This will give you the correct units and account for the total volume of the solution.

Next, make sure to use the correct units for each variable. For example, if you have the total mass of the solution in grams, you will need to convert it to moles using the molar mass of NaCl (58.44 g/mol). Similarly, if you have the total volume of the solution in milliliters, you will need to convert it to liters.

Lastly, when calculating the total mass of the solute, make sure to subtract the mass of the solvent from the total mass of the solution. This will give you the mass of the solute alone.

As for hands-on methods, you can try evaporating the solvent from a known volume of the solution and then measuring the mass of the remaining solute. This will give you a direct measurement of the mass of the solute in the solution.

I hope this helps and good luck with your experiment!