New answers tagged physical-chemistry
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Can an oxidising/reducing agent oxidise/reduce itself?
A simple example can be the disproportionation of chlorine when bubbling a current of chlorine gas $\ce{Cl2}$ into a solution of $\ce{NaOH}$ (containing $\ce{OH^-}$ ions):
$$\ce{Cl2 + 2 OH^- -> ...
- 24.4k
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How can I measure the energy contained within water vapor?
The absolute values of internal energy $U$ or enthalpy $H$ (which could be more useful for water vapour) at a single state point are meaningless. It is only the difference between two different state ...
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Why is the local coupling constant (vibronic coupling) given in eV?
The local coupling constant is typically given in units of energy, such as electronvolts (eV), because it represents the strength of the coupling between the electronic and vibrational degrees of ...
- 407
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Volume of a solution in terms of molality, molar mass and density
The equation given is
$$V = \frac{1000 + m \cdot M}{d} \pu{cm3}$$
It only works if you know to enter the quantities' numerical values after expressing them in the conventional units (g for mass, mol/...
- 34.5k
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Volume of a solution in terms of molality, molar mass and density
Recall the definitions of molality and molarity, it is mol solute / kg of solvent and mol solute/ Vol of solution in (L). It is not kg of solution in molality. Instead of memorizing a plug and chug ...
- 36.1k
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What is the difference between distillation temperature and boiling point?
Boiling point and distillation point are similar if we take a glance but the significant difference among them..
Boiling point
When a liquid starts converting into its gaseous state and the constant ...
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What is the difference between distillation temperature and boiling point?
Both depend on the composition of your sample (keyword Raoult's law), as well as the external pressure.
One may argue the term boiling point leans more toward the characterization of a compound (e.g., ...
- 24.7k
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Length of a 1D box in hexa-1,3,5-triene
For this type of question, we not only consider the length of the bonds between the carbon atoms, but we also have to add on the atomic radii at both ends of the structure. I assume the atomic radii ...
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More minerals in seawater at greater depths?
There are huge differences in water composition (and temperature) where there are undersea feature such as hydrothermal vents. The heat and particulates can be "detected as far as tens to ...
- 26k
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Electron orbitals
[OP ...] that would mean they can be found right next to the nucleus
They are close to the nucleus at times. The nucleus is tiny compared to the dimensions of a bond (or an atomic radius), so the ...
- 34.5k
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Electron orbitals
Classical analogies about simple orbits don't describe electron behaviour well
Thinking about electrons as having "orbits" is rarely helpful as their behaviour only makes sense in a quantum ...
- 33.7k
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Electron orbitals
Can electrons be found anywhere within the space described by a 3D orbital "90% of the time" (as stated in my textbook)?
Yes, they can.
But that would mean they can be found right next to ...
- 32.4k
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Electron orbitals
Yes. The electron has a small but not zero possibility to stay quite near the nucleus, and for example at a smaller distance than the traditional radius of the first 1s orbital. The probability of ...
- 24.4k
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Why does a symmetric stretch mode not have an imaginary frequency?
The path over the transition state is like an inverted parabola so has a negative frequency, i.e. its an upside down harmonic oscillator if you like. But orthogonal to this is a second potential like ...
- 28.1k
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Why does a symmetric stretch mode not have an imaginary frequency?
Below is a sketch of the atomic arrangements when considering a linear attack.
The blue diagonal represents the symmetric stretch. The reaction coordinate (dotted line) takes the lowest possible path ...
- 34.5k
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What is the pKa Range for weak acids and bases?
What is the pKa Range for weak acids and bases?
Bases don't have a $\mathrm{p}K_\mathrm{a}$. To discuss the strength of a base, you can look at the $\mathrm{p}K_\mathrm{a}$ of the conjugate acid, ...
- 34.5k
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What processes generate entropy as heat flows across temperature gradient
For steady state heat conduction in the slab between the source and sink, we have $$\frac{d}{d x}\left(k\frac{d T}{d x}\right)=0$$where k is the thermal conductivity. If we divide this equation by ...
- 12.3k
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Claim that the temperature of steam is not the boiling point on a stovetop?
There is a saying that "Paper never refused ink", the same goes for the web. At 1 atm pressure, if you boil water, and water vapor exist at equilibrium and the vapor pressure of water is ...
- 36.1k
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Claim that the temperature of steam is not the boiling point on a stovetop?
In everyday life the term boiling generally means the nucleation and growth of bubbles of steam. Typically in a saucepan or a kettle the water is heated from below and the bubbles of steam form on the ...
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Can we calculate van der Waals' constant a for the following case?
First, there is a mistake in the fifth expression. It should be written $$PV' + P'V = RT$$
Second, it is not clear what Siddharth is looking for. If he wants a way of calculating $a$ with other van ...
- 24.4k
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Question about entropy generated in isothermal expansion of an ideal gas
Let $T_B$ be the temperature of the interface between the surroundings and the system. For an ideal surroundings reservoir (typically assumed), the entropy change of the surroundings is $\Delta S_{...
- 12.3k
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how helium can be compressed if its compressibility factor is alway greater than 1?
If $Z$ > $1$, it means that, when compression this gas, $pV > nRT$. This is the only meaning. It does not mean that the gas cannot be compressed.
- 24.4k
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how helium can be compressed if its compressibility factor is alway greater than 1?
You have an incorrect interpretation of the compressibility factor $Z$. $Z$ being greater than unity does not mean that it cannot be compressed. All gases can be compressed (that is a part of the ...
- 36.1k
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Why does water evaporate spontaneously at room temperature despite ΔG > 0?
I think the starting assumption is not correct.
Water does not always evaporate.
For instance, at night, the temperature decreases due to radiative cooling. If the temperature drops to the dew point ...
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How are fundamental equations valid for both reversible and irreversible processes?
The starting equation should read $dS>dq/T_B$, not dS>dq/T, where $T_B$ is the temperature at the boundary between the system and surroundings (usually an a reservoir temperature) through which ...
- 12.3k
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