Mass Spectroscopy
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Joined: 13/05/2013 - 23:18
Posts: 1
Mass Spectroscopy

I really, really need help with this question. It's been killing me for the past hour :(

When reacted with a small quantity of water, SiCl4 produces an oxychloride X, SixClyOz. The mass spectrum shows peaks at mass no. 133,149,247,263, and 396. (Assume all species contain the 16O, 28Si and 35Cl isotopes only.)

a. Deduce the molecular formula of X

b. Suggests the fragments responsible for the peaks at the mass numbers 133, 247 and 263

c. Hence suggest the displayed formula of X

Help please :)

Joined: 10/06/2007 - 22:31
Posts: 347
I'd rather not give answers

I'd rather not give answers but I am happy to give clues.

Of Si, Cl, O only Cl has an odd mass number so that tells you something about the 396 peak, it must have an even number of chlorine atoms.

So, the 396 peak must contain either 2Cl (70), 4Cl (140), 6Cl (210) or 8Cl (280)

The other peaks must have odd numbers of Cl atoms in them.

Then try a few guesses to see how the numbers come together.

eg  149 + 247 = 396

We might expect four bonds on each Si, two bonds on each O and one bond on each Cl (but don't be over certain of this because this might be a compound that doesn't fit this pattern).

Try the mass number combinations of things like Si + 2Cl + O and see if you can make these add up to the masses of the fragments.

No more clues for now, come back later.



Joined: 28/07/2013 - 04:59
Posts: 1
mass spctrosccopy

this mass spectroscopy is really difficult for me. I haven't understood anything.

help pleasecrying