Timeline for Chemical formulas with non-integer coefficients
Current License: CC BY-SA 4.0
10 events
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| Feb 22, 2022 at 9:15 | comment | added | matt_black | @theorist This may be the source of the confusion here. I answered the question (which was about how fractional formulae make sense). The Maurice answer brings in a whole bunch of evidence about a specific compound (making assumptions based on the compound that are not justified in general about formulae like this). Hence confusion: the question was about a general principle, not this specific compound. | |
| Feb 22, 2022 at 9:12 | comment | added | matt_black | @Maurice The disagreement between us may arise because you are providing an answer based on this specific compound not one based on the question which is about how fractions arise in chemical formulae in general. Nothing in the formula says alloy but alloys are a common example of where such formulae arise. Any specific knowledge of this compound is not relevant to the general answer and adding it is confusing. | |
| Feb 22, 2022 at 9:11 | comment | added | theorist | @matt_black I believe Maurice is right about the composition of this specific compound—and, correspondingly, the meaning of its formula—because it's not a simple combination of Hg, Cd, and Te. Rather, it's a combination of HgTe and CdTe. Hence its composition is always (HgTe)_(1-x) + (CdTe)_x, and thus its composition is always constrained as Hg_(1−x)Cd_xTe. See: en.wikipedia.org/wiki/Mercury_cadmium_telluride | |
| Feb 22, 2022 at 8:54 | history | edited | Maurice | CC BY-SA 4.0 |
added 7 characters in body
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| Feb 22, 2022 at 8:20 | comment | added | Bruce | 132pm vs 144pm not the same, but perhaps substitutable without too much change in arrangement? | |
| Feb 21, 2022 at 22:18 | comment | added | Maurice | @matt_black. Who tells you it's an alloy ? It may be a compound like $\ce{ZnS}$ where $\ce{Zn}$ has been replaced partly by $\ce{Cd}$ (30%) and partly by $\ce{Hg}$ (70%), which are all in the same 12th column. And where the sulfur $\ce{S}$ atom is replaced by $\ce{Te}$, which is also in the same 16th column. | |
| Feb 21, 2022 at 19:44 | comment | added | matt_black | But what people want to know for an alloy is the atomic proportions of the whole alloy, not just the proportion of the ingredients other than the commonest one. Eg the whole alloy has 35% Hg not 70%. Nothing in the formula says that a version of this alloy couldn't have more Hg than Te, just that this version of the alloy doesn't. | |
| Feb 21, 2022 at 19:35 | comment | added | Maurice | Les coefficients $0.7$ and $0.3$ are not depending on the proportion of $\ce{Te}$. For each Te atom, there is $x$ atom $\ce{Hg}$ and ${1-x}$ atom Cd | |
| Feb 21, 2022 at 17:33 | comment | added | matt_black | The formula doesn't mean that: it simply describes the relative atomic composition. And you have miscalculated the proportions for the whole compounds as you ignored the proportion of Te. | |
| Feb 21, 2022 at 16:49 | history | answered | Maurice | CC BY-SA 4.0 |