What Does the Molar Composition in Crystal Synthesis Mean?

[ch3m]

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?

 

[Borek]

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.

 

[ch3m]

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?

 

[Borek]

Looks OK.

 

[LudusRex]

Hello,

Thank you for sharing your concern. Based on the information provided, it appears that the reaction mixture molar composition is indeed referring to the moles of each compound present in the solution. This would mean that they have a large amount of water in the solution, which is not uncommon in crystal synthesis reactions.

It is possible that the excess water is necessary for the reaction to occur or for the desired crystal structure to form. Further information on the purpose of the water and the reaction conditions would be helpful in understanding the reasoning behind the molar composition.

Additionally, it is important to note that the molar composition may not always add up to exactly 1 due to rounding or experimental error. However, the proportions of each compound in the mixture should still be accurate.

I hope this helps clarify the situation. If you have any further questions or concerns, please do not hesitate to ask.

Best,