[nightingale]

Hello

I am interested in structures of hydrates and I want to get information about some hydrate former guest molecules. The reason why I am writing here is to ask whether there is some way of finding the molecular sizes of molecules, such as carbon tetrachloride, trichloroethylene, 1,1,2-trichlorotrifluoroethane and tetrachloroethylene. I will be glad if anyone can recommend a computer program or method to determine the molecular sizes. Thanks:)

[xiankai]

check out the chemical formula/element composition of the substances, then look up their defined mass number and add them all up together.

eg. carbon tetrachloride = CCl₄,  1 carbon atom = 12.0107 g/mol, 4 chlorine atoms = 35.432 g/mol.

add them all up and u get 153.7387g, the mass of 1 mole of CCl₄.

[nightingale]

check out the chemical formula/element composition of the substances, then look up their defined mass number and add them all up together.

eg. carbon tetrachloride = CCl₄,  1 carbon atom = 12.0107 g/mol, 4 chlorine atoms = 35.432 g/mol.

add them all up and u get 153.7387g, the mass of 1 mole of CCl₄.

Thank you for your reply Indeed, I need the molecular size, not the molecular weight. I want to find out the diameter of the molecules in angstrom. However, I do not know how to do

[xiankai]

oops im sorry!

now this is beyond my knowledge >_>

[Borek]

Precise measurements are done use using some X-Ray methods on crystals.

For less precise results - most bonds have known length and most atoms have known radius, drawing the structure and applying simple gemetry should be enough. However, your task is poorly defined - what is a diameter of a molecule if the carbon chain can change it's shape? What is a diameter of ball? Of rugby ball? Of cigar?

[nightingale]

Precise measurements are done use using some X-Ray methods on crystals.

For less precise results - most bonds have known length and most atoms have known radius, drawing the structure and applying simple gemetry should be enough. However, your task is poorly defined - what is a diameter of a molecule if the carbon chain can change it's shape? What is a diameter of ball? Of rugby ball? Of cigar?

Thanks for your answer I actually want to determine if some molecules will occupy the cavities of the hydrate molecules. There exist 3 types of hydrate structures and the ratio of the molecular diameter to cavity diameters makes it possible to determine the stability of the hydrates for different structure types. Some of the diameters of molecules exist, such as C2H6, which is stated as 5.5 angstrom. However, I don't know how to find the diameters of some molecules such as carbon tetrachloride, 1,1,2-trichlorotrifluoroethane, trichloroethylene and tetrachloroethylene. Thanks again:)

[Hcurious]

Maybe this is too simplistic but you might be able to get a rough idea of the size as follows: look up the density, you know the molecular weight, that gives you the moles in one cc; from Avogadro's number that gives you a rough estimate of the volume occupied by one molecule. Take the cube root of that for an estimate of the molecular size.