Why doesn't a solute add to the volume of a solution?  [ENDORSED]

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Crystal Rivera 2J
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Why doesn't a solute add to the volume of a solution?

Postby Crystal Rivera 2J » Tue Dec 02, 2014 10:35 am

In molarity, it is calculated by taking moles over TOTAL VOLUME. For problems in the past, we use the volume of the solvent as if the solute didn't add to the volume. Does the solvent not add any volume to the solution? Why not?

Patrick Chin 1F
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Re: Why doesn't a solute add to the volume of a solution?

Postby Patrick Chin 1F » Tue Dec 02, 2014 5:22 pm

Yes, in the real world we would also calculate the volume added by the solute. However, the volume is so little that it is negligible in our calculations.

Christopher Lew 1L
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Re: Why doesn't a solute add to the volume of a solution?

Postby Christopher Lew 1L » Thu Oct 01, 2015 8:55 pm

That is right, the change in volume when the solute is added is so small that there is basically no significant change to the overall volume.

Chem_Mod
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Re: Why doesn't a solute add to the volume of a solution?

Postby Chem_Mod » Thu Oct 01, 2015 9:00 pm

Molarity is moles solute divided by TOTAL volume. Not the volume of solvent. This is why when preparing a standard solution, one adds solid to the flask THEN fills it up to the mark. Not the other way around because this would cause the total volume to exceed the mark. However, in the end the difference between these two is small.

KELLY COSTA 1J
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Re: Why doesn't a solute add to the volume of a solution?

Postby KELLY COSTA 1J » Wed Oct 07, 2015 10:16 am

Although the solute does have a mass, it is very small and negligible. In real life it may affect the volume, but for the problem's sake we can just assume it attains a mass of 0.

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Re: Why doesn't a solute add to the volume of a solution?  [ENDORSED]

Postby Chem_Mod » Tue Jun 21, 2016 4:02 pm

For the purpose of this class, we will assume the solute is dissolved in the solvent and contributes negligibly to the total volume.

In real life, the volume contribution by the solute in the solution is complicated. Molecular interactions and molecular forces play a vital part and depending on the nature of these interactions, the solute can decrease or increase the volume. Thus, the proper way of preparing the solution is to dissolve the solute into the solvent and then fill to the mark, as posted earlier in this thread.

Yixiao Hu 3C
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Re: Why doesn't a solute add to the volume of a solution?

Postby Yixiao Hu 3C » Sun Oct 07, 2018 11:02 pm

Compared to the volume of the solution, or to the solvent, the volume of your solute is so tiny; at the same time, the solute will dissolve in your solvent. So the solute will not account to the volume of a solution.


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