All Questions

16
votes
3answers
16k views

Why do Magnesium and Lithium form *covalent* organometallic compounds?

Lithium and magnesium are Group 1 and Group 2 elements respectively. Elements of these groups are highly ionic, and I've never heard of them forming significantly covalent inorganic compounds. Yet ...
16
votes
2answers
1k views

By what reaction does (–)-sparteine decompose in ambient conditions?

In its pure form (–)-sparteine is an only-slightly-yellow clear, viscous liquid. Yet, after only a week of being kept in dry, normal atmosphere (in a round bottom flask covered by a septa), some of it ...
2
votes
1answer
3k views

Is soap the natural form of Sodium Lauryl Sulfate?

I was told that "Sodium Tallowate, sodium cocoate and sodium palm kernelate are the 'natural' forms of SLS". Is this true? I thought "natural" SLS would be SLS derived from a natural product such as ...
6
votes
2answers
1k views

What is it about the relationship between the Fe²⁺ and Fe³⁺ in magnetite that makes it diamagnetic?

Hematite is composed of $\ce{Fe2O3}$, and is paramagnetic, whereas magnetite is $\ce{Fe3O4}$ and is diamagnetic. Magnetite's nature is due to the presence of both $\ce{Fe^{2+}}$ and $\ce{Fe^{3+}}$ (...
25
votes
7answers
14k views

Why is AgCl less soluble than AgNO₃?

Related: Reaction between silver nitrate and aluminum chloride Experimentally, $\ce{AgCl}$ is insoluble in water, but $\ce{AgNO3}$ is soluble. They're pretty common in a lab (well, $\ce{AgCl}$ is a ...
21
votes
4answers
39k views

what kind of suspension liquid should be used with ferrofluid (so it does not stain the glass)

Please take a look at the following video: I am working on a new project, and I need to find whats the best liquid to hold ferrofluid inside the glass (or maybe even plastic) container, so that ...
7
votes
2answers
4k views

How long does it take to run a MS/MS experiment

I am not planning to do these types of experiments but I would like to know the order of magnitude of the time it takes to run an LC-MS/MS experiment. Let's assume that I have the sample prep (protein)...
4
votes
1answer
120 views

Solution based measurement of Solvent-Accessible Surface Area of macromolecules

The Solvent-Accessible Surface Area (SASA) is a valuable metric for looking at protein folding and protein-protein interactions. However, this measurement is typically done by calculating the SASA ...
12
votes
2answers
1k views

Why is slush hydrogen at the triple point?

Slush hydrogen is a mixture of liquid and solid hydrogen at the triple point considered as a possible vehicle fuel. What is the need of having it at the triple point? Couldn't any other set of ...
10
votes
1answer
3k views

What's the difference between precipitate and turbidity?

In many tests for various radicals, a "<color> precipitate" or "<color> turbidity" is mentioned. For example, lead ...
8
votes
2answers
22k views

Why are strong acids and bases not suitable as primary standards?

This is one of the questions with which I have puzzled over, and can arrive at no definite conclusion. Why are strong acids or bases, such as $\ce{H2SO4}$,$\ce{ HNO3}$, $\ce{HCl}$, and $\ce{NaOH}$ not ...
-16
votes
3answers
27k views

Temperature of pure oxygen combustion [closed]

What is the temperature of pure oxygen being combusted? I was wondering about it.
7
votes
1answer
250 views

Rotation energy barrier for carboxypyrazolate

In this molecule, which is 3,5-dimethyl-4-carboxypyrazolate (unless I got it wrong): I do not think there is free rotation around the bond indicated in red, because one can write a resonance ...
7
votes
2answers
135 views

How to understand this form of writing the solution: (some salt • n H₂O)?

For example — "high purity chloride salt of Zinc $(\ce{ZnCl2.2H2O})$" or "various concentrations of $\ce{FeCl2.4H2O}$". What does the number before $\ce{H2O}$ mean?
11
votes
3answers
14k views

Reaction between silver nitrate and aluminum chloride

I googled a bit about what $\ce{AgNO3 + AlCl3}$ will yield and found out the following: $\ce{3AgNO3 + AlCl3 -> Al(NO3)3 + 3AgCl}$ Why is that? I know that $\ce{Ag}$ is higher up in the reactivity ...
16
votes
1answer
3k views

Why does gum get harder to chew after a while?

My Sister asked me this: "Why is it that when we chew gum, it is soft and mushy to begin with , but slowly gets firmer and firmer like after 20 mins of chewing?" I think it is because when we ...
8
votes
1answer
222 views

What does the charge distribution around a Stone-Wales defect look like?

I'm reading a book on carbon nanotubes (P.J.F. Harris, Carbon Nanotube Science, to be specific) at the moment and puzzling about Stone-Wales or 5775 defects. This is where two adjacent carbons undergo ...
21
votes
1answer
435 views

Is the Springborg 6D phase space model used in modern molecular orbital modeling?

In a series of papers in the early 1980s, Michael Springborg explored an interpretation of the Wigner phase space function as an electron density in a six-dimensional $(q,p)$ phase space. He applied ...
39
votes
8answers
43k views

Is iron in the brown ring compound in a +1 oxidation state?

In the standard brown ring test for the nitrate ion, the brown ring complex is: $$\ce{[Fe(H2O)5(NO)]^{2+}}$$ In this compound, the nitrosyl ligand is positively charged, and iron is in a $+1$ ...
-6
votes
1answer
1k views

How to compute molecular formula?

I have the following question to solve: Tungsten, $\ce{W}$, and chlorine, $\ce{Cl}$, form a series of compounds with the following compositions: \begin{array}{rr} \text{Mass % W} & \text{...
4
votes
1answer
679 views

Predict XPS Spectrum of Organic Monolayers on a Semiconductor

X-ray photoelectron spectroscopy (XPS) is a particularly useful technique for examining the surfaces of all sorts of materials. Organic monolayers are particularly difficult to characterize completely ...
4
votes
1answer
465 views

How is silica bead bonded into polystyrene?

What kind of bonds silica bead forms with polystyrene? Silica is now as ~100 $\mu$m spherical particles in bulk polystyrene that is made by melting. How can I bond the silica particles more tightly ...
8
votes
1answer
103 views

Has QTPIE ever been applied to 1D metals such as polyacetylene?

QTPIE is a fluctuating charge model that substantially improves modeling of polarization and charge transfer. I was curious whether it has ever been applied to 1D metals such as polyacetylene to ...
14
votes
1answer
5k views

How are $\sigma$ and $\sigma^\pm$ determined in Hammett plots?

The Hammett plot is commonly invoked in organic chemistry to reason about the plausibility (or implausibility) of various reaction mechanisms. The vertical axis is essentially the logarithm of an ...
8
votes
1answer
654 views

Why are there no edge dislocations in a face-centered cubic (FCC) lattice?

In crystallography, we know that the Burgers vector is parallel to the dislocation direction in a screw dislocation, and perpendicular in a edge dislocation. Furthermore, I have in my lecture notes "...
20
votes
2answers
25k views

Why are the majority of cleaning solutions basic?

When testing for pH for common household cleaning products, such as dishwasher fluid, I noticed that majority of them tend to be basic? Why is that? Do acid make good cleaning solutions as well?
8
votes
1answer
928 views

What is the difference between an angular and linear skeletal formula?

When drawing a skeletal formula, what is the difference between an angular version and a linear version? I was asked to draw the Z isomer of Resveratrol: For which I drew: However the markscheme ...
23
votes
5answers
897 views

Why are equations of state for a non-ideal gas so elusive?

The ideal gas equation (daresay "law") is a fascinating combination of the work of dozens of scientists over a long period of time. I encountered Van der Waals interpretation for non-ideal gases ...
3
votes
2answers
10k views

Why does activated carbon preferentially adsorb anions?

Brands like Brita and Pur (in the U.S.) have made a name for themselves for the ability of their product (essentially a large-pore filter with activated carbon/charcoal) to extract the added chlorine ...
17
votes
2answers
5k views

Not your ordinary hard water deposit

We have a well that delivers hard water and we do not have a water softener. (There was a “green sand filter” that utilizes permanganate to oxidize other metals on the system, but it has been ...
26
votes
3answers
19k views

Why does ice cream make soda fizz?

I've noticed that adding a chunk of ice cream to soda makes the soda fizz slightly near the soda-ice cream interface. I thought it was a physical effect due to the temperature, but adding ice has no ...
10
votes
2answers
5k views

How does one recognized Td/Oh symmetry in molecules?

The identification of point groups of a molecule is usually done following a strict scheme, either manually or algorithmically. In all textbooks I could find, however, the first step of the scheme is ...
18
votes
1answer
644 views

When simulating spectral line broadening, which convolution is preferred?

Many computational chemistry packages permit the calculation of vibrational and electronic spectra. These spectra are obtained as a set of discrete eigenvalues however they are often convolved with ...
3
votes
1answer
4k views

Can dissolution reactions be endothermic?

Is it possible for a dissolution reaction of the form $$\ce{X(s) ->[solvent] X (solv)}$$ or $$\ce{M_mX_x (s) ->[solvent] m M^x+ (solv) + x X^m- (solv)}$$ to be endothermic, i.e. $\Delta_\...
14
votes
1answer
17k views

Resolution in Mass Spectrometry

I have been reading about resolution in mass spectrometry and there are a few things I do not understand. The resolving power is determined by $m/(m_2-m_1)$ at full width half height of a peak. The ...
5
votes
1answer
434 views

Mercury, amalgams and mercury compounds [closed]

Mercury is toxic. It forms amalgams and inorganic mercury compounds/salts are available. My question is on toxicity. I am interested in its toxicity, not the mode of action (as it will be part of ...
16
votes
1answer
2k views

What do typical results from inductively coupled plasma mass spectrometry (ICP-MS) look like, and how do I interpret them?

I have a degree in chemical engineering and remember having seen a inductively coupled plasma mass spectrometer (ICP-MS) during the laboratory part of a chemistry course I took while at university, ...
5
votes
4answers
16k views

What is the difference between melting and dissolving?

What is the difference between melting and dissolving? I am looking some general features. The answer should be adaptable to the melting/dissolving of ice cube (water) in a class of pure alcohol (...
13
votes
1answer
3k views

How are turbostratic graphite phases formed?

Turbostratic graphite is graphite in which there is quenched rotational disalignment between adjacent graphene sheets, i.e. one sheet is rotated with respect to its neighbor. I suppose this could be ...
11
votes
3answers
640 views

Should one pronounce “periodic” the same in “periodic acid” and “periodic table”?

In “periodic table”, the adjective is related to the noun period, and comes from Ancient Greek περίοδος through French périodique. In “periodic acid”, it is formed from the prefix per- and iodic (like ...
18
votes
1answer
567 views

Why does benzene bend in this reaction?

From here I can see why hapticity changes here, but not why it is necessary for the benzene ring to bend. The resonance energy of benzene is pretty large, and there's no balancing increase in ...
12
votes
1answer
2k views

Why is the benzyne triple bond distorted?

In many places I've seen the "extra" bond in benzyne being labelled as $\ce{sp^2-sp^2}$ overlap or distorted (not parallel) $\ce{p\pi-p\pi}$ overlap. But I've failed to see why we can't have a normal, ...
31
votes
3answers
2k views

Pauli exclusion principle and resonance

I've always been a bit uncomfortable with the concept of more than two electrons in a single orbital-like region(probability-wise) which occurs in resonance. This seems to disobey Pauli's exclusion ...
18
votes
1answer
1k views

What dictates the lifetime of a solvated electron in a given solvent?

Solvated electrons have a long lifetime in ammonia solutions, but their counterparts in water (called hydrated electrons) have a much smaller lifetime, of the order of microseconds in very pure water. ...
8
votes
1answer
109 views

Where do I find datasheets of zeolites?

I'm looking into uses of zeolites as water absorbers for heat storage and absorbtion cooling. However, I don't find hard numbers on the likes of absorption enthalpies at different temperatures, ...
6
votes
2answers
905 views

Z-matrix of a series of 5 colinear atoms

How can I write a Z-matrix for the following complex? O==C==O H--O \ H I have managed to write: ...
14
votes
1answer
126 views

Is there a theory behind selecting elements that may be successful in potential superconductors?

Looking at something like $\ce{YBa2Cu3O7}$ which was one of the first cuprate superconductors to be discovered, I'm always curious how the selection of these substances as likely superconductors comes ...
17
votes
1answer
3k views

Definitions of autocatalysis

Is there a formal definition or algorithm that can take a list of reactions and tell me whether it contains a set of species that can produce itself autocatalytically? It is clear that the following ...
10
votes
2answers
7k views

Gas chromatography/mass spectrometry: Can I use peak ratios and molecular mass to derive quantity?

Can derive the quantity of a substance from a GC/MS report if I know: the ratio to another substance in the data, the quantity of that second substance, and the molecular mass of both substances. ...
6
votes
2answers
141 views

Is a 2-D periodic structure isomorphic with the surface of a torus, a sphere, neither or both?

When I was reading through the ADF-BAND tutorials, one of the toy systems presented was a 1-D periodic structure involving 3 collinear hydrogen atoms. The tutorial pointed out that, topologically ...

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