DavePhD
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What is the pH of ice?
46 votes

According to Martin Chaplin's Water Dissociation and pH: In ice, where the local hydrogen bonding rarely breaks to separate the constantly forming and re-associating ions, the dissociation constant ...

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

According Kinetics, Mechanism, and Spectroscopy of the Reversible Binding of Nitric Oxide to Aquated Iron(II). An Undergraduate Text Book Reaction Revisited The correct structure is $\ce{ [Fe^{III}(...

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Can 100% covalent bonds exist?
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35 votes

According to Pauling's famous The Nature of the Chemical Bond , 3rd edition, at page 73: In the hydrogen molecule a quantum-mechanical treatment has shown that the two ionic structures $\ce{H+H-}$ ...

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Can we really see the bonds?
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34 votes

All credit to Zhang et al. "Real-Space Identification of Intermolecular Bonding with Atomic Force Microscopy" Science Vol. 342 no. 6158 pp. 611-614. Yes, direct images of bonds, not only covalent ...

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Why does whipped cream use nitrous oxide instead of nitrogen gas?
28 votes

According to Nitrous oxide, carbon dioxide, and their mixtures as propellants, Proc. Chem. Specialties Mtrs. Assoc., June 1950, page 45, William Strobach, $\ce{CO2}$ and $\ce{N2O}$ are both suitable ...

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What is more acidic: D3O+ in D2O or H3O+ in H2O and why?
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25 votes

For the reasons explained in New point of view on the meaning and on the values of $K_\mathrm{a}(\ce{H3O+, H2O})$ and $K_\mathrm{b}(\ce{H2O, OH-})$ pairs in water Analyst, February 1998, Vol. 123 (409–...

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Why is the definition of the mole as it is?
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25 votes

Why is the definition of the moles as it is? It is a rather arbitary definition that the mole is the number of atoms in 12g of carbon 12. This has not always been the definition. For example, prior ...

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Is there a difference between NaCl or table salt (processed) and salt from the Himalayas?
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24 votes

No salt will be pure NaCl. Each will have some degree of other elements. The fact that the salt isn't white confirms there are other elements present. See Analysis of Gourmet Salts for the ...

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Can drinking a lot of water be fatal?
21 votes

Yes. See Jury Rules Against Radio Station After Water-Drinking Contest Kills Calif. Mom The husband of a California woman who died after participating in a radio station's water drinking contest ...

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What's the strongest known organic acid?
21 votes

According to "The Strongest Isolable Acid" Angewandte Chemie International Edition 43 (40): 5352–5355, carborane acids are the strongest, with $\ce {H(CHB11Cl11)}$ being the strongest. Depending ...

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PV=nRT approximation on other planets?
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20 votes

The differences in acceleration due to gravity is not the main factor in comparing how accurate the approximation is for each planet. The main factor is the mass of gas each planet's atmosphere ...

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Oxidation state of the sulfur atoms in the thiosulfate Ion
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19 votes

According to Oxidation state of sulfur in thiosulfate and implications for anaerobic energy metabolism according to the currently held view, the two sulfur atoms of thiosulfate exist in the ...

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What is the pKa of the hydronium, or oxonium, ion (H3O+)?
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19 votes

The controversy surrounding the $\mathrm{p}K_\mathrm{a}$ of hydronium mostly arises from the definition of $K_\mathrm{a}$ or lack thereof. There is no IUPAC definition of $\mathrm{p}K_\mathrm{a}$ ...

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Do electrons have some volume, area or shape?
18 votes

Quoting from the Nobel lecture of Hans G. Dehmelt (1989): With the rise of Dirac’s theory of the electron in the late twenties their size shrunk to mathematically zero. Everybody “knew” then ...

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Why is methanol toxic?
18 votes

The enzyme alcohol dehydroganase converts the methanol to formaldehyde in the body. Formaldehyde is then converted to formic acid. Formaldehyde can cause blindness before being converted to formic ...

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Realistic chemical spill accident in high school chemistry class
17 votes

The real high school accidents that I know of involved flammable liquids (ethanol or methanol) igniting. Mishaps in school labs reveal lack of safety (PDF link) Two high school kids burned in lab ...

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Why is NaCl3 possible?
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17 votes

Yes NaCl3 is possible. Think of the more common iodine analog. $\ce{KI + I2 -> KI3}$ For a comprehensive analysis see: Unexpected stable stoichiometries of sodium chlorides At 25-48 GPa, ...

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What is the usage of orbitals more complex than f orbitals?
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17 votes

Surprisingly, I learned that there are also usages for orbitals g,h,i and even j. Actually, the letter "j" is not used, so it is s, p, d, f, g, h, i, k, l, etc. The higher angular momentum ...

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Is hydrogen bonding generally defined to include only three period two elements?
Accepted answer
16 votes

I don't think there is any such traditional definition requiring $\ce{N}$, $\ce{O}$ or $\ce{F}$. For example, in table 7 and the discussion thereof in Hydrogen Bonding Annual Review of Physical ...

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Does the hydrogen ion actually exist?
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16 votes

Yes free $\ce{H+}$ ions, protons, really exist. Protons are constantly emanating from the sun and reaching Earth. The proton flux is continuously monitored by satellite. However, in a ...

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How do I visualize an atom?
16 votes

I am looking for a 3 dimensional visualization of a whole (moderately complex, hydrogen is just a ball) atom that includes 3 dimensional orbital geometry. 3 dimensions is only enough to represent the ...

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Salts that are more hydrophilic than NaCl
16 votes

The scale for degree of being hydrophilic is contact angle. Contact angle ranges from 0 to 180 degrees, 0 being the most hydrophilic and 180 being the most hydrophobic. 180 degrees means that a ...

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How to RAISE the melting point of water?
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16 votes

source One way to raise the melting point of water is to increase pressure beyond about 635 MPa. By raising pressure you could get the melting point to be even greater than the normal boiling point. ...

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Why is water "the universal" solvent?
16 votes

Just to provide an alternative answer: Consider a solvent miscibility table like the one linked. What is the least miscibile solvent? Water! Water is the worst solvent. Water is immiscible with 17 ...

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What is the Structure of FeSO₄ • NO?
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16 votes

What is the structure of $\ce{FeSO4 \cdot NO}$ that is formed when $\ce{NO}$ is passed through ferrous sulphate solution? The structure is octahedral. The Fe ion is at the center of the octahedron. ...

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Is cis dipole moment is always greater than trans dipole moment?
Accepted answer
15 votes

No. The dipole moment of trans-cyclooctene ($\pu{0.82 D}$) is greater than cis-cyclooctene ($\pu{0.43 D}$). See On the Molecular Geometry of trans-Cycloöctene, J. Am. Chem. Soc. 1958, 80 (8), 1953–...

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Why isn't water an ionic compound?
15 votes

No compound is purely ionic. Water is about 33% ionic. Linus Pauling discusses the ionic character of water in his famous "The Nature of the Chemical Bond" [1] at pages 100-101. Pauling says as a ...

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Is there a simple way to separate deuterium oxide from tap water?
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15 votes

It depends how pure you want the $\ce{D2O}$ to be and what you consider simple :) Electrolysis of water strongly favors "H" being converted to hydrogen gas rather than "D", by a factor of about 8 to ...

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What is active mass?
15 votes

The term "active mass" is a historical term. The concept of an equilibrium constant was developed by Cato Maximilian Guldberg and Peter Waage. The Law of Mass Action has also been referred to as the ...

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Do bare protons exist, even transiently, in aqueous solution?
15 votes

According to Myths about the proton. The nature of H+ in condensed media Accounts of Chemical Research, vol. 46, pp 2567–2575: But to put this into perspective, an electron-free proton has an ...

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