Sandbox II has become as clogged as Sandbox I was (and is), especially for users with 10,000 reputation or above. So, here is a new new post...
Before you delete a post here, please reduce it to one line without MathJax.
Old formatting sandboxes:
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$\begingroup$ Why do we have to reduce it to one line without MathJax? $\endgroup$– MicelleJun 19, 2020 at 14:53
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9$\begingroup$ @Micelle deleted posts are viewable by users with >10,000 reputation, so it's just a courtesy thing. Long mathjax posts make the page load slowly. $\endgroup$– orthocresolJun 19, 2020 at 14:55
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1$\begingroup$ @orthocresol, moving your comment explanation into the question would improve it. $\endgroup$– Ray ButterworthFeb 9, 2022 at 15:00
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11 Answers
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Somebody complained that the reaction I asked about doesn't exist. Why is this a problem?
Chemistry is an experimental science first and foremost, and this is especially true of synthetic chemistry, whether organic or inorganic.
What this means is that: we don't come up with theories from first principles, then use them to predict reactions. [We're getting better at doing this using quantum mechanics, but it's still very early days.] Instead, we find out that a reaction happens, and then we work backwards to come up with a model that explains it.
The ultimate source of "truth" in chemistry is not defined by our theories, but rather by our experimental observations. The theories only exist because they can explain experimental evidence.
[Incidentally, that's why there are so many exceptions to the theories. Many of them have a limited range of validity, in that they can only explain a certain subset of the experimental observations we have. A simple example is the octet rule. It works for quite a lot of organic molecules, but can completely fall apart in other contexts.]
So, asking "why does this reaction occur?" is only sensible if that reaction has actually occurred!
If nobody has done it before in real life, then we have no way of knowing whether it would actually occur. And secondly, if it doesn't actually occur and we come up with a theory to explain it, then there is no guarantee that that theory would be correct.
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Common misspellings
This table is indexed alphabetically in the first column. Please feel free to add to it.
The second column contains a link to the appropriate Wikipedia page.
| Wrong | Correct | Remarks |
|---|---|---|
| Breddts | Bredt’s [rule] | Julius Bredt. |
| carbonation | carbocation | Carbonation is what you do to make fizzy drinks. |
| Clemenson | Clemmensen [reduction] | Erik Christian Clemmensen. |
| die | dye | “Die” is only for “die Farbstoffe”. Or the singular of “dice”. |
| Diel's Adler | Diels–Alder [reaction] | Otto Paul Hermann Diels; Kurt Alder. |
| fajan's | Fajans’ [rules] | Kazimierz Fajans |
| flourine | fluorine | |
| Friedel–Craft's | Friedel–Crafts | The guy's name was James Crafts, not James Craft. |
| gasses | gases | One outgasses gases. |
| Gibb's | Gibbs [energy] | Josiah Willard Gibbs. |
| Henderson–Hasselbach | Henderson–Hasselbalch [equation] | Lawrence Joseph Henderson; Karl Albert Hasselbalch. |
| iconic | ionic [bond] | |
| morality | molarity | The moral of this story is that only people can be moral or amoral. |
| Nerst | Nernst [equation] | Walther Hermann Nernst. |
| phosphorous | phosphorus | This refers to the element (as a noun, not adjective). See also next entry. |
| phosphorus acid | phosphorous acid | This refers to the acid $\ce{H3PO3}$. See also previous entry. |
| pie | pi/π [bond] | Pie bonding is for SeasonedAdvice.SE. |
| seperation | separation [process] | “Seperate” is not even an English word. |
| stigma | sigma/σ [bond] | Stigma bonding is for Christianity.SE or MedicalSciences.SE. |
| Tollen's | Tollens’ [reagent] | Bernhard Tollens. |
| Vander-Wal's, Van der walls | van der Waals [force] | Johannes Diderik van der Waals. Note it's lowercase “v”. |
| Vant-hoff | van 't Hoff [equation] | Jacobus Henricus van 't Hoff. |
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Temporary place to get answers and such put together. Everything I post here will be deleted in a couple of days or so. A tidy sandbox is a good sandbox!
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1$\begingroup$ Cheers Ed, I've screenshotted this! I use Engineering Equation Solver (EES) so should be able to get something going in there :) $\endgroup$ Aug 13, 2022 at 3:12
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$\begingroup$ The Volta condensing electroscope is based on the electrophorus. Exp 132 works because the Volta condensing electroscope acts as a voltage multiplier thus the small voltage produced by a cell ($\approx \rm V$) is magnified hundreds of times. Think of a condenser charged so that the potential difference across the plates is $1\,\rm V$ and then the separation of the plates increased one hundred fold. Charge the same, capacitance decrease by a factor of 100. $\endgroup$– FarcherJul 4 at 22:21
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$h=\frac{I_{\text{const}}\cdot R_{\text{ref}}(1+\alpha\Delta T)}{A_{\text{filament}}(T-T_{\text{flow}})}$
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$\begingroup$ Do you still need this? I've upvoted it only so that it stops triggering this question to get bumped up by the "community user". $\endgroup$ Sep 26, 2022 at 19:22
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1$\begingroup$ @user1271772 I don't need it anymore, I guess. What do you want to do? Remove all the answers? Delete the post itself? In any case, I don't mind a post getting bumped all the time in meta. Just saying. $\endgroup$ Sep 27, 2022 at 6:52
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The following are the definitions of 'mole' represented in the form of equations:
(1) Number of moles of molecules $=\frac{\text { weight in } g}{\text { molecular weight }}$
(2) Number of moles of atoms $=\frac{\text { weight in } \mathrm{g}}{\text { atomic weight }}$
(3) Number of moles of gases $=\frac{\text { volume at NTP }}{\text { standard molar volume }}$ (Standard molar volume is the volume occupied by 1 mole of any gas at NTP, which is equal to $22.4$ litres.)
(4) Number of moles of atoms / molecules / ions / electrons $=\frac{\text { no. of atoms } / \text { molecules } / \text { ions } / \text { electrons }}{\text { Avogadro constant }}$
(5) Number of moles of solute $=$ molarity $\times$ volume of solution in litres or no. of millimoles = molarity $\times$ volume in $\mathrm{mL}$.
$\frac{\text { Millimoles }}{1000}=$ moles
(6) For a compound $\mathrm{M}_{\mathrm{x}} \mathrm{N}_{\mathrm{y}}, x$ moles of $\mathrm{N}=y$ moles of $\mathrm{M}$
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$\begingroup$ Do you still need this? I've upvoted it only so that it stops triggering this question to get bumped up by the "community user". $\endgroup$ Sep 26, 2022 at 19:22
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| Substance | $\Delta H^\circ_\mathrm{f}$ / $\pu{kJ mol-1}$ | $\Delta G^\circ_\mathrm{f}$ / $\pu{kJ mol-1}$ | $S^\circ_\mathrm{f}$ / $\pu{J mol-1 K-1}$ |
|---|---|---|---|
| $\ce{CH4(g)}$ | $-75$ | $-51$ | $186$ |
| $\ce{CO(g)}$ | $-111$ | $-137$ | $198$ |
| $\ce{CO2(g)}$ | $-394$ | $-394$ | $214$ |
| $\ce{H2O(l)}$ | $-286$ | $-237$ | $70$ |
| $\ce{H2O(g)}$ | $-242$ | $-229$ | $189$ |
| $\ce{O(g) }$ | $249$ | $232$ | $161$ |
| $\ce{O2(g) }$ | $0$ | $0$ | $205$ |
| $\ce{O3(g) }$ | $143$ | $163$ | $239$ |
| $\ce{H2(g)}$ | $0$ | $0$ | $131$ |
| $\ce{C(s)}$ | $0$ | $0$ | $6$ |
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2$\begingroup$ :P Well, if you'll forgive me: the negative numbers should be written with actual minus signs, hyphens are a bit shorter. IMO the easiest is to just use MathJax for everything, i.e. do
$-75$, that will automatically use minus signs and also makes the font a bit more consistent throughout. $\endgroup$ Apr 19, 2022 at 12:24 -
$\begingroup$ @orthocresol Next thing, I'll worry about left or right justification of the items... $\endgroup$– Karsten ModApr 19, 2022 at 12:38
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$\begingroup$ Yeah, it would be nice to have the numbers aligned after the negative sign! $\endgroup$ Apr 19, 2022 at 12:40
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$\begingroup$ @KarstenTheis My take on this is to align numbers by a decimal point and flush them right. Since MD tables are r̶̶e̶̶t̶̶a̶̶r̶̶d̶̶e̶̶d̶̶ limited in terms of formatting options, just align the numbers right with
|--:|and, if applicable, round them up to the same decimal point so that one can easily visually compare the values. Also, I think missing values are better denoted with "NA" rather than with an em dash, and a slash serves a better (and mathematically correct) separator for quantity symbols and units in a header. $\endgroup$– andselisk ModApr 19, 2022 at 12:58 -
1$\begingroup$ @andselisk I am learning more today than my students this entire semester. I changed it to "0" instead of "NA" for the elements in their most common allotrope. $\endgroup$– Karsten ModApr 19, 2022 at 14:39
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1$\begingroup$ @KarstenTheis One more thing: if you have a choice, it's better to use a font with monospaced numbers. Zero wiggle in character length assists a lot with the visual comparison of long numbers. $\endgroup$– andselisk ModApr 19, 2022 at 15:55
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$$ \begin{comment} Commented code \end{comment} $$
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$\begingroup$ $%comment$ $%comment$ $%comment$ $%comment$ $%<comment>$ $%comment$@Avogadro, comment doesn't seem to be the right environment to use for this.
$%comment$would render better. It doesn't exist in MathJax from what I see. $\endgroup$ Oct 26, 2022 at 15:30
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$%<Comment>$ "<>" renders in answers but not in comments?
Comment to Avogadro's post here. Worked in my comments
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$\begingroup$ Do you still need this? I've upvoted it only so that it stops triggering this question to get bumped up by the "community user", but that wasn't enough because the score was -1! $\endgroup$ Sep 26, 2022 at 19:22
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$\begingroup$ @user1271772 Funny that someone would downvote this :/ $\endgroup$ Sep 27, 2022 at 6:50
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I've noticed references to the $(k)$ for the saponification reaction above to be about $$\frac{6}{M\hspace{5 pt}min}$$ or slower. Which would mean at 0.1 M concentrations, while the reaction happens faster, it could still be observed. We could further this ability by decreasing the temperature further as well.
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$\begingroup$ You could do:
$\pu{6 M-1 min-1}$$\pu{6 M-1 min-1}$ to get the units upright correctly -- there's also the MathJax faq which gives a nice bunch of examples chemistry.meta.stackexchange.com/q/86/16683. $\endgroup$ Oct 24, 2022 at 15:12 -
$\begingroup$ Thanks! I really appreciate this! I don't know why I was trying to put M^-1, I think that's because of the
mhchemplugin. I'm definitely trying to drink water from a firehose when it comes to learning LaTeX and mhchem all at once! :-) Thank you @orthocresol. $\endgroup$ Oct 24, 2022 at 15:18 -
$\begingroup$ No prob -- generally, in LaTeX (and MathJax) if your exponent consists of more than one characters you need braces, so
$\mathrm{M}^{-1}$would give you $\mathrm{M}^{-1}$. To typeset the whole quantity correctly, with just built-in commands, you'd need something like$6~\mathrm{M}^{-1}~\mathrm{min}^{-1}$$6~\mathrm{M}^{-1}~\mathrm{min}^{-1}$. The\pucommand is basically syntactic sugar for this. (Though, if it was an actual LaTeX document, most people would recommend thesiunitxpackage... that's an entirely different story!) $\endgroup$ Oct 24, 2022 at 15:41