Gas with greatest molecular weight

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Discussion Overview

The discussion centers around identifying the gas with the greatest molecular weight at room temperature, exploring various candidates and their properties. The scope includes theoretical considerations and properties of specific chemical compounds.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that radon (Rn) has a high atomic weight of 222, positioning it among the heaviest gases.
  • Another participant proposes that heavy-metal hexafluorides might hold the record, specifically mentioning tungsten hexafluoride (WF6) with a molecular weight of 298 g/mol.
  • A different participant mentions platinum hexafluoride (PtF6) as having a molecular weight of 309 g/mol, but notes that it is a solid at room temperature.
  • There is a discussion about the state of PtF6, with one participant highlighting its limited liquid range and questioning its classification as a gas at room temperature.
  • Another participant brings up uranium hexafluoride (UF6) and plutonium hexafluoride (PuF6) as potential candidates, noting that they are gases just above room temperature, with boiling points in the 30s or 40s Celsius.

Areas of Agreement / Disagreement

Participants do not reach a consensus on which gas has the greatest molecular weight at room temperature, with multiple competing views and candidates presented.

Contextual Notes

There are limitations regarding the definitions of "room temperature" and the states of the mentioned compounds, as well as the specific conditions under which they are considered gases.

Loren Booda
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What room-temperature gas has the greatest molecular weight?
 
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Atomic weight of Rn is 222. That's right up there with the giants.

I think the record is held by one of the heavy-metal hexa halides. The halide ions provide a nice repulsive shield.
 
Could be WF6 (tungsten hexafluoride) at 298 g/mol.
 
Since we're talking metal fluorides, PtF6 = 309 g/mol
 
shrumeo said:
Since we're talking metal fluorides, PtF6 = 309 g/mol

But it's a solid at room temp. In fact it is liquid only from 63C to 69C, a pretty small range, wot ?
 
yeah, i guess 70C would be a pretty hot room
well, if we want to stretch it a little UF6 and PuF6 are dern heavy and gases right above room temp, if I'm not mistaken (again) their boiling points are in the 30s or 40s.
 

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