BMAT Q

Tritiated water, HTO decays by beta radiation.

What forms?
a) HeOH
b) He + H2O + O2
c) He + H2O + H2

The answer given is b.

My thoughts:
3T -> 3He + e-
Therefore HTO -> HeOH+ + e-(ejected from molecule). In this case the HeOH+ ion involves a normal covalent bond between the He and the O, so isn't so bonkers. But it is not HeOH, so (a) is wrong. It wouldn't be too stable and the likey thing to drop off would be and He leaving OH+, this (with an O with 2e- missing) would accept a lone pair on an HTO forming H2TO2+, which would lose H+ OR T+ forming H2O2 OR HTO2, which would slowly decompose into H2O or HTO + O2 - is this where they were going with (b)?

Then there is the issue with the self ionisation of water: HTO <-> H+ + OT- OR T+ + OH-. These could re-cross-combine forming H2O OR T2O. I suspect this thinking is a bit of a dead-end.

But... where does the beta e- go? If it was re-captured by HeOH+ the He would definitely fall off, releasing OH radicals, which are not easy to get rid of, when there are only H2O type molecules to react with - unless there were lots of OH radicals, then you could form H2O2 type molecules. BUT HeOH+ won't exist for long. Neither would OH+. The longest surviving positive species would be H+, which would lead to H radicals, which would either pair up, forming H2 (which apparently is wrong) or with rare OH radicals forming H2O.

The biggest problem I have with the Q is the half life of T being 11 years!

Our best answer was that (a) and (c) were do unlikely that (b) is the best worst answer.