What Does the Molar Composition in Crystal Synthesis Mean?

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Discussion Overview

The discussion revolves around the interpretation of molar composition in a crystal synthesis reaction mixture, specifically the meaning of the reported values for various compounds including SiO2, Al2O3, NaCl, and H2O. The scope includes conceptual clarification and mathematical reasoning related to chemical synthesis.

Discussion Character

  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether the reported molar composition represents mols of each compound in solution, noting that the large amount of water suggests a significant volume.
  • Another participant agrees with the interpretation of the values as mols and speculates that the reporting method might be a convention in certain papers.
  • A later reply proposes using the molar ratios derived from the reported values to calculate the necessary amounts of each compound based on a fixed volume of water.

Areas of Agreement / Disagreement

Participants generally agree on interpreting the values as mols of each compound, but there is uncertainty regarding the reporting convention and the implications of the large water volume. The discussion remains unresolved regarding the exact meaning and application of the molar composition.

Contextual Notes

There are limitations regarding the assumptions made about the reporting convention and the calculations based on the molar ratios, which have not been explicitly validated.

ch3m
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Hi guys,
I'm facing a problem.
I've read a paper where they tried to synthesise a crystal and they give the following reaction mixture molar composition:
3.0 SiO2
1.0 Al2O3
0.1 NaCl
276 H2O

What does it means?
It can't be the molar fraction since the sum of all the fraction must give 1 as result.
I guess that it should be the mol of each compound in solution, but that means that they have almost 5 L of water... am I right?
 
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ch3m said:
I guess that it should be the mol of each compound in solution, but that means that they have almost 5 L of water... am I right?

That's how I would read the information.

No idea why they reported it this way, perhaps that's a convention used in such papers.
 
Borek said:
That's how I would read the information.

No idea why they reported it this way, perhaps that's a convention used in such papers.

Thanks.

So can I take such values as a ratio??

I mean: 3.0:1.0:0.1:276

So if I fix a volume of 250 ml of water which means 13.877 mol, I need to divide the mols for 276 and then multiply for the ratio.
i.e. for Al2O3 --> 13.887*(1/276) and for NaCl 13.887*(0.1/276)
Right?
 
Looks OK.
 

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