Jan
  • Member for 7 years, 5 months
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  • Hesse, Germany
Brown stains on skin after working with Tollens' reagent
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55 votes

The stains are due to silver nitrate, the reactive portion of Tollens’ reagent. It is very prone to reduction to metallic silver. If you got it on your hands (a clear signal you weren’t wearing ...

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Why is pyrimidine less basic than pyridine?
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42 votes

It is not the number of lone pairs that in any way explains basicity. Take a random sugar and it will have ten times the number of lone pairs (albeit on oxygen, not on nitrogen) without being ...

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How do organic chemistry mechanisms become accepted?
37 votes

This doesn’t exactly concern the actual mechanism you asked for, but as part of my PhD thesis, I performed an amide alkyne coupling the mechanism of which had been researched by Arndt et al.[1] ...

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Does the term 'Cation' always refer to a positively charged particle?
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32 votes

Yes, cations always have a positive charge and anions always have a negative one. The difficulty is that the term cathode and anode do not always correspond to the same pole. The cathode is that pole ...

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Which one is the best notation for sodium acetate
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31 votes

There is nothing wrong with either formula. And you can use even more: $\ce{NaC2H3O2}$ $\ce{C2H3NaO2}$ It really depends on which point you want to bring across. $$\ce{NaCH3COO}$$ This formula, ...

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Won't the net effect of a catalyst be zero if it creates a new path with lower activation energy?
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30 votes

Your realisation is correct and something chemistry teachers try to hammer into their students’ heads time and time again (and yet, the point is still often lost): Catalysts will never change the ...

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Why is ammonium a weak acid if ammonia is a weak base?
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27 votes

First, let’s get the definition of weak and strong acids or bases out of the way. The way I learnt it (and the way everybody seems to be using it) is: $\displaystyle \mathrm{p}K_\mathrm{a} < 0$ ...

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Why is the cyanide ion toxic?
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27 votes

Cyanide is a pretty good ligand for coordination compounds. The electron pair on carbon (which, incidentally, also carries the Lewis structure’s formal charge) is located in the HOMO — much like as in ...

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Emergency shower for nitric acid spills
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27 votes

If you spill nitric acid onto the table, you yourself are unharmed and you can use a cool head to decide what to do next. If the spill is small, pour water on it to both dilute it and dilute the heat —...

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Why does carbon monoxide have a greater affinity for hemoglobin than oxygen?
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25 votes

Excursion into simple coordination chemistry: Bonding, backbonding and simple orbital schemes Please refer to Breaking Bioinformatic’s answer for the MO scheme of carbon monoxide, it is very helpful. ...

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Why is '-ethane' in 'methane'?
24 votes

It’s worth pointing out how much of a coincidence it is that the modern ethyl and methyl are identical but for one letter. While Karsten already outlined the general bits of etymology behind these two ...

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Has anyone even taken a picture of a molecule to confirm the geometry predicted by theory?
24 votes

In addition to the answer provided by Todd, there is also the very established technique of single crystal X-ray diffraction. The basic principle is sending X-rays through a single crystal of a ...

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Is it possible for one specific atom in a molecule to have a non-integer oxidation state?
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24 votes

It depends. Consider various radicals such as the superoxide anion $\ce{O2^{.-}}$ or $\ce{NO2^{.}}$. For both of these, we can draw simple Lewis representations: In these structures, the oxygen atoms ...

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Will adding up protons and electrons (without neutrons) create a new element?
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23 votes

Yes and no. Elements are defined by the number of protons only. It does not matter if (say) a carbon nucleus has six or seven (or eight) neutrons, they will all react the same.* With that, to create ...

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Burns from boiling water and steam
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22 votes

Let’s consider the following cases: getting $1\,\mathrm{mol}$ of $100\,\mathrm{°C}$ water on one’s skin getting $1\,\mathrm{mol}$ of $100\,\mathrm{°C}$ air on one’s skin getting $1\,\mathrm{mol}$ of $...

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Why is 1H-borepine aromatic?
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21 votes

1H-borepine is isoelectronic to the cycloheptatrienyl cation. In both cases, you have a planar ring of seven atoms, whose hybridisation is close enough to $\mathrm{sp^2}$ to allow for a third p-...

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Explanation for why nickel turns green in hydrochloric acid
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20 votes

The question is really badly worded. For starters, let’s look at solutions of nickel(II): Figure 1: Nickel(II) solutions. From left to right: $\ce{[Ni(NH3)6]^2+}$, $\ce{[Ni(en)3]^2+}$, $\ce{[NiCl4]^2-...

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Is there a mnemonic to study the spectrochemical series?
19 votes

I would not recommend a mnemonic for the spectrochemical series for a number of reasons: Often, it depends on both metal and ligand and coordination geometry how big a certain splitting is. The ...

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How can the gauche-effect be explained?
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19 votes

The gauche effect is commonly explained with LCAO-based bond orbitals. LCAO is short for linear combination of atomic orbitals and implies that we can take two atomic orbitals $\phi_1, \phi_2$ and ...

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What do the prefixes meta, ortho, pyro mean in inorganic chemistry?
18 votes

Are there any terms and conventions I should be aware of? Yes. IUPAC publishes the Red Book also called Nomenclature of Inorganic Chemistry which is the authoritative source of nomenclature terms. ...

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Can an amide nitrogen be a hydrogen bond acceptor?
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18 votes

If I understood you correctly, you are talking about the peptide bond nitrogens ($\ce{R-C(=O)-\color{red}{N}H-R}$). This is, reduced to its significant chemical functional group an amide, more ...

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Hybridization of nitrogen in trisilylamine, (SiH3)3N?
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18 votes

Ordinarily and according to Bent’s rule, we would expect nitrogen’s lone pair to be in an $\mathrm s$ orbital and nitrogen using its three $\mathrm p$ orbitals to form three bonds to the three silicon ...

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Why is the Vitamin B complex, a "complex"?
18 votes

It is essentially exactly what your teacher says: the term vitamin B complex is used because the structures assigned a name ‘vitamin Bx’ don’t really have anything in common although they are all ...

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Does acetic acid give a positive result with the iodoform test?
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18 votes

The iodoform reaction proceeds by the mechanism shown below. (The final proton transfer need not occur between the two partners, any other hydroxide could abstract the acid’s proton and any water ...

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Why can NCl3 be hydrolyzed but CCl4 cannot?
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18 votes

There are a few (mis-) conceptions in the question that require addressing other than giving the simple (yet correct) answer that permeakra gave. $\ce{NCl3}$ The hydrolysis of this compound is ...

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Where did amino acids get their one-letter codes?
17 votes

Some single letter codes that aren’t the amino acid’s starting letter actually make sense when viewed from certain angles. Here’s the list starting with the bloomin’ obvious: G — Glycine A — Alanine ...

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Why isn't aluminium involved in biological processes?
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17 votes

The metal’s trivalency is certainly not an issue. Iron and cobalt form trivalent compounds (in the $\mathrm{+III}$ oxidation state) in many of their biologically relevant complexes. In fact, in ...

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Jahn-Teller Distortions in Square Planar Complexes?
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17 votes

Introduction Thank you for prompting me to look for square planar complexes that are not $\mathrm{d^8}$; I learnt some valuable stuff while researching the answer to this question! Do take this ...

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Why is the Haber process carried out at such high temperatures?
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17 votes

As others have pointed out, it is purely kinetics, but you may still wonder, why. For a reaction to actually occur (in both directions) and thus for an equilibrium to be reached, you need to overcome ...

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Why is there no neutron in protium?
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17 votes

Your chemistry teacher is making a few simplifications there that make the statement false on a black-and-white true-and-false scale. Protons would repel each other electrostaticly due to their same ...

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