Buck Thorn
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Linear algebra and Hess's law?
24 votes

To convert this into a generic linear algebra problem you'd rewrite it in the form $Ax=b$ where $A$ is a matrix of stoichiometric coefficients of size $m \times n$; $x$ is a vector of length n of ...

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Strange Sticky Substance on Digital Camera
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23 votes

After the lengthy back and forth perhaps an official answer is due: the blue salt deposit on the camera battery holder door is most likely copper(II) hydroxide by reaction of leaked alkaline battery ...

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Is there an uncertainty associated with the value 0 K for absolute zero?
20 votes

As another answer explains, absolute zero is defined in the Kelvin temperature scale as precisely $\pu{0 K}$. But this is not the entire story, as all measurements have an associated uncertainty (all ...

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Why does radiocarbon dating only work in nonliving creatures?
15 votes

There are plenty of good sources online explaining the principle behind radiocarbon dating. For instance, the wikipedia explains: During its life, a plant or animal is in equilibrium with its ...

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How are the Van der Waals constants a and b related to each other?
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14 votes

Yes, they are certainly correlated as shown in the following plot based on data from the Wikipedia Van der Waals constants data page The correlation should not be entirely surprising: the covolume ...

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What is an example of chemical reaction that can be assisted by both an inorganic catalyst and an enzyme?
13 votes

A good example is the conversion of hydrogen peroxide to oxygen and water $$\ce{2H2O2 ->2H2O + O2}$$ It can be catalyzed by catalase, which has one of the highest known turnover numbers, or by an ...

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Uses of Fourier / Laplace transforms in chemistry (apart from spectroscopy)
13 votes

The Fourier Transform is important in many applications beyond spectroscopy, for instance in computational and theoretical chemistry. One example encountered in learning chemistry is in quantum ...

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If change in free energy (G) is positive, how do those reactions still occur?
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13 votes

$\Delta G^\circ_m$ is the difference in molar Gibbs free energy between the reagents and products in their standard states (in the case of $\ce{AgI(s)}$, the standard state for the reagent is the pure ...

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Can a long polymer chain interact with itself via van der Waals forces?
13 votes

You have a possible answer to your question in proteins, an example which includes some long polymer chains. Intramolecular interactions - while not necessarily the driving force for formation of a ...

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What is the physical significance of the universal gas constant R?
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12 votes

Charles' law says that at constant pressure the volume and temperature of an ideal gas are related as $$\frac{V_1}{T_1}=\frac{V_2}{T_2}$$ If $V_2=V_1+dV$ and $T_2=T_1+dT$ then $$\frac{V_1}{T_1}=\frac{...

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Can someone intuitively explain the reason for the units of entropy (J/K )?
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11 votes

The units of of energy over temperature (e.g. J/K) used for entropy in the thermodynamic definition follow from a historical association with heat transfer under temperature gradients, in other words, ...

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Why does ordinary water have a triple point?
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11 votes

Summarizing the relevant point (pun intended) of my answer to a related post: a mixture does not exhibit a "triple line" if its composition is constant. It is only a "triple line" ...

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Quantifying soapiness; there's pH, pKa and pO2, is there a p_soap or p_surfactance?
10 votes

A concept that captures how effective a detergent is at doings its job is aptly called "detergency." As might be expected this is a complex property and difficult to describe unambiguously ...

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What is the difference between "vapour" and "gas"?
10 votes

I'm surprised the OED has such a strict definition for gas. I could not find a strict definition in the IUPAC color books (certainly not in the gold book). Presumably these words are in such common ...

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Oxygen Solubility in Water
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10 votes

Oxygen is relatively insoluble in water, its solubility being only 264 µM at 25 °C. That explains in part why you (and fish) require dedicated oxygen carriers in your blood to transfer sufficient ...

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Does sulfoxide H₂SO exist?
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10 votes

This is not an answer to the question "can the sulfoxide be synthesized in significant yield" (and under which conditions). Instead, this is a "naive" prediction based on the data you provide and two ...

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How do I figure out how many hydrogens my compound actually has using a mass and NMR spectrum?
10 votes

Being an NMR fan myself I would inspect that NMR spectrum: The integrals suggest you have 11 $\ce{^1H}$ or a multiple thereof (the number under each peak is the normalized integral, which is ...

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How can I find out a substance name based on its structural formula?
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10 votes

That's betanin, from which beets derive much of their deep purple color, and which may have neuro-protective (Ref. 1) features. The following is the structure retrieved from the wikipedia (on 2019-10-...

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Isn't the change in Gibbs free energy for a reversible process zero?
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9 votes

The cycle shown is a classic reversible Carnot cycle. An intuitive reason for the change in Gibbs free energy not being equal to zero for such a step is that the pressure is not constant: the internal ...

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Clarification of textbook concepts relating to "perfect", "ideal", and "real" gases
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9 votes

The authors attempt to explain that in many sources the term "ideal gas" is used in place of "perfect gas" to indicate a gas following the ideal gas law and which has the property that the molecules ...

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Why do glow-in-the-dark substances dim gradually?
9 votes

There are two potential questions here: one is why is dimming a slow drawn-out process (incoherent, unlike a "switch"). The second question is why different stars may appear to lose their intensity at ...

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Melting point of aspirin, contradicting sources
9 votes

The CRC Handbook of Chemistry and Physics ($\mathrm{86^{th} Ed.}$, section on Physical Constants of Organic Compounds) provides an MP of $\pu{135^\circ C}$ for aspirin (2-(Acetyloxy)benzoic acid). ...

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Why can't the energy of an electron exceed 0 eV?
8 votes

The value of the energy in the Bohr model is zero when the quantum number is infinity because that is the limiting value of the Coulombic potential at large distances, and because the electron is ...

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What are the limitations of the Hendersson-Hasselbalch equation?
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8 votes

The key approximation made in deriving the Henderson-Hasselbalch equation is that the equilibrium constant can be written as $$K=\frac{c_{H^+}c_{A^-}}{c_{HA}}$$ that is, we assume activity ...

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Why is the dz2 orbital so different from the rest?
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8 votes

The wikipedia is helpful in explaining why radial variations should arise in the density of non-s orbitals: The non radial-symmetry properties of non-s orbitals are necessary to localize a particle ...

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Is it possible to build a non-degrading battery?
8 votes

But is it possible to have a battery that will never degrade and always keep its performance without upkeep/maintenance? Well, consider the dry pile powering the Oxford Electric Bell, which has been ...

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What does the state of a substance at a specific T and P mean?
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7 votes

I will start by addressing the posted question: the "state of a substance at a specific temperature and pressure" refers to "the most stable phase of the homogeneous substance at the ...

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What happens to boiled (BMIM)PF6?
7 votes

Ionic liquids have very special properties, the most important of those of interest is that they are liquids at low temperature with extremely low vapour pressure. This is in fact the main reason they ...

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How can a thermometer ever show the actual temperature of an object if the object loses heat to the thermometer?
7 votes

For the question to have a concrete answer you would have to explain in more detail how the temperature is to be measured and how the thermometer and sample interact with the surroundings. If you use ...

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Why do the first and second laws of thermodynamics not contradict each other?
7 votes

Entropy is not energy. Entropy times temperature has energy units. Entropy can be regarded as a statistical property of thermodynamic systems. Although such a definition is not necessary to apply the ...

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