Questions tagged [physical-chemistry]

Study of macroscopic and microscopic phenomena in chemical systems in terms of physical laws and concepts [thermodynamics, statistical mechanics, kinetic theory, quantum mechanics...].

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27 views

Explain how chemical bond energy is ultimately converted to electrical energy

I can understand how a cell develops emf, why the electron flows between the battery terminals. I do not understand, How the chemical bond energy is transformed to electrical energy? What are the ...
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1answer
33 views

Why is an electrodes standard reduction potential does not depend on amount of chemicals?

The standard reduction potential is fixed for the type of chemical reaction. Why is it so? Why is an emf of a cell or an electrode's Standard reduction potential does not depend on say, quantity of ...
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3answers
152 views

Natural log of 2 in Radioactivity half life?

How exactly was the half life equation $\frac{ln2}{\lambda}$ derived? My book states something about integrated rate laws but doesn't really explain anything. Sorry, this is my first post in Physics ...
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38 views

Converting a discrete statistical energy distribution to a continuous version

The probability of finding a particle at a particular energy level when energy is considered discrete is according to Boltzmann: $$P(E_j) = \frac{g_j\cdot e^{-\beta E_j}}{\sum_{j=1}^\infty g_j \cdot ...
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1answer
46 views

When we burn a wood it burns with flame although it do not contain any gaseous substance [duplicate]

In books it is given that flame is only produced when gaseous substance burn but when dry wood is burnt it also burn with flame.why.
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2answers
93 views

Temperature as function of $CO_2$

The carbon stored in fossil fuels must have been taken out of the earth atmosphere from CO2 in past periods by plants. Thereby reducing the amount of CO2 drastically and increasing the amount of O2 to ...
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1answer
82 views

How to calculate the mass of gas needed to fill a cylinder to a certain pressure?

I m tasked with a tricky situation. I need to calculate the exact amount a tank can take in gas. But I dont know the volume of the tank. I just need to make sure that the tank reaches the right ...
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1answer
59 views

Why do the wavelengths of lights oscillate wrt atmospheric penetration?

Funnily enough, I was reading about Jungian Archetypes when I happened upon this diagram: I had not previously seen this and I couldn't find much information on it nor why it is occurring, I'd ...
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6answers
2k views

Conservation of Mass and Energy [duplicate]

I was thinking about some physics (relativity in particular), when it suddenly occurred to me that all my life I had been balancing chemical equations assuming conservation of mass, but I was ...
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44 views

Faradays constant determination? [closed]

I am a bit confused on how faraday determined his constant. So I’ve been taught that he realized that if you sent a certain amount of charge (96485 C), then one mole (or some fraction of that based on ...
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1answer
43 views

Selection rules in rotational spectroscopy- water molecule

The University of Liverpool maintains a ChemTube 3D page, where it says http://www.chemtube3d.com/spectrorotcd0-CE-TEST-ROTATE-ALL.html *> Highly symmetric polyatomic molecules, such as carbon ...
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57 views

Why is absorbance calculated as $\log_{10}(1/R)$ and not $1-R$?

According to Lambert Beers law, the absorbance ($A$) of a sample at a given wavelength can be described in terms of its transmittance ($T$) according to: $A = \log_{10}(1/T)$ In near-infrared ...
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34 views

Is there a definition for describing nuclear material undergoing fission/fusion? [closed]

Is there a term similiar as a piece of coal burning as ambers? Can nuclear material undergoing the reaction be transported?
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3answers
126 views

Why is methane considered an important greenhouse gas?

Methane’s absorption bands are centered at 3.2 and 7.2 microns -- far off the peak of the Planck spectrum for a 290 K blackbody near 16 microns. Moreover, its absorption bands overlap with the water ...
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2answers
105 views

If one divides the molecular dipole of HCl by the interatomic separation, the result is not a multiple of the electron charge. Why is that?

I'm having some trouble understanding the reasoning behind the final note in the following worked problem: An HCl molecule has a dipole moment of $3.4\times10^{-30}\:\rm C\:m$. Assuming that equal ...
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1answer
113 views

Time evolution of molecular signal from a laser-induced plasma - finding the right model for my data

I am looking at molecular emissions in laser-induced plasma plumes created in argon at reduced pressure (in the mbar range). To be precise, these are heteronuclear diatomic molecules that emit ...
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35 views

Mathematical Resolution of Overlapping Signals

I would like to take the opinion of physicists (my area is chemistry). During instrumental analysis, the output is a instrument response vs. time. Each peak corresponds to a molecule which is ...
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2answers
57 views

Why are there less bubbles the second time I pour soda in the cup?

I poured some Pepsi into a mug, and it foamed, and I poured until the foam was at the top of the glass. I waited a few seconds for the bubbles to go, and the liquid level was revealed to be at around ...
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1answer
32 views

Specific Heat, Conservation of Energy, and Kinetic Energy

Different molecules have different specific heats, such as water, which has a very high specific heat due to strength of inter-molecular attractions. If temperature is the random kinetic energy of ...
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2answers
83 views

Finding partial molar volume from an algebraic expression

I'm given the equation $ V = 120X_1 + 70X_2+X_1X_2*(15X_1+8X_2)$ and told to calculate $\bar V_1 $ & $ \bar V_2$ and then to show that $ V = \Sigma_i X_i*\bar V_i$. Since there are two mol ...
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1answer
142 views

Why hot soup is tastier than cold soup? [closed]

My physics teacher recently asked me this question. Can anyone answer the question?
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3answers
73 views

Bicycle Fuel equivalent on l/100km

Is there a way I can calculate the equivalent how much a Human powered bicycle consumes in the equivalent l/100 Km of Diesel fuel? And also can I calculate the same for Gasoline fuel? And for ...
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47 views

Van der waals forces interaction

My slides say: A gas with low density in which you can consider the attractive energy the sum of the isolate atoms couple $$ u=\int^S_\sigma{4\pi\frac{N}{V}}\left(\frac{\beta}{r^6}\right)r^2\...
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11answers
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Are there physical properties that can be used to differentiate stainless steel from copper in a home environment? [closed]

So the backstory is that I purchased a reusable drinking straw that is copper coloured, but is advertised to be stainless steel. That got me thinking about whether I could be sure it was one or the ...
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0answers
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Bond Nature of a comound [closed]

How can we determine the type of Bond in LiBaPO4? can we find out the nature of bond through charge transfer values of these elements? if yes then how?
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Gibbs free energy the 3 equation confusion

Hello can you please help me with thermochemistry? I have been taking chem classes since highschool and they ALL talked about Gibbs free energy, enthalpy, and entropy... even in college I got away ...
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41 views

Why hydrogen bond forming has lifetimes on picosecond scale?

According to this Research http://www.kinetics.nsc.ru/mds/downloads/2009_JSC_Naber_Vol_LifeTime.pdf hydrogen bonds are formed and destroyed within a timescale of a few picoseconds. Why hydrogen ...
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1answer
30 views

Nucleus in the wires

Can someone explain why we consider the electrons to move through a wire and not the nucleus? Couldnt atoms get ionised with losing a proton?
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15 views

Potential energy of molecule [duplicate]

Does potential energy of molecule and therefore bond length change with temperature?
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25 views

Bond energy and tempetature

Does bond energy depend on temperature? Also why is it defined at 298 Kelvin if some substances cant be in gas phase in that temperature?
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44 views

Why are(n’t) rechargeable batteries damaged by partial charging?

Originally asked in ElectricalEngineering.SE, but I was told Physics.SE might be a better place to ask. Over the years, I've come across websites and people with different opinions on the "correct" ...
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1answer
33 views

How will the Big Rip affect chemistry and nuclear interactions?

The "Big Rip" is a theoretical scenario for the death of the universe. Let's assume that this scenario is true. What can we expect to happen to chemistry and nuclear interactions in the time ...
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1answer
34 views

Charge density of sea water

If sea water contains salt ions and some H+ and OH- ions, what are the charge density of a certain volume of sea water? And is there a way to calculate?
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1answer
47 views

Why doesn't lithium form di-lithium crystals? (Calling Mr.Spock)

Hydrogen is in the first column of the periodic table. At STP it is a di-atomic gas. When cooled and/or under pressure it forms a crystalline solid of di-hydrogen molecules. Calculations indicate ...
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375 views

Why is argon a noble gas but not, say, beryllium or palladium?

Why is argon a noble gas given that the 3d subshell is still empty? More generally, why is it that the filling of a p sub-shell makes an element noble rather than s, d, or f sub-shells, or completed n-...
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40 views

Constant pressure

When we refer to constant pressure like in Charles law what is this pressure? The pressure of the gas or the pressure that the container (the piston maybe) exert on the gas? Also does atmospheric ...
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2answers
69 views

What is the energy of an atomic orbital?

When we refer to energy of an atomic orbital what is this energy ? is potential energy ? but if is potential energy then shouldn't be considered the whole potential energy of the atom ( potential ...
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1answer
57 views

What are some molecular systems which have quantum states that are measurably incompatible?

What I'm looking for is a molecular system, which we can produce in a lab, that is, A discrete variable system (ie, a finite dimensional hilbert space) It has observables that are incompatible with ...
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4answers
7k views

Why doesn't water actually perfectly wet glass?

According to many high school textbook sources, water perfectly wets glass. That is, the adhesion between water and glass is so strong that it is energetically favorable for a drop of water on glass ...
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1answer
58 views

When putting water on two pieces of paper they bond. Is that due to van der Waals bonds?

I've been wondering what keeps two pieces of wet paper together when in contact. Does water have any adhesive property? Or does it decompose something from the paper and creates some kind of glue? I ...
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1answer
40 views

Interaction between molecules

Does the interaction with enviroment change the geometry of a molecule ? for example in H2O the angle betwen H-O-H is 104.5 degrees. Does this angle change for example if the molecule of water is near ...
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46 views

Chemical potential of a reaction

I often see two various forms of the species $i$ chemical potential $\mu_i$ in a chemical reaction, in terms of enthalpy of formation $\Delta h_{f,i}^0$ and standard state entropy $s_i^0$. My ...
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30 views

What are the specific heats of Dysprosium in its gas phase?

What are the specific heats of Dysprosium in its gas phase? The handbook of chemistry and physics [1], is a single volume of 1500 pages containing all the information an experimentalist would need ...
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1answer
28 views

Hydrogen oxygen fuel cells

In hydrogen - oxygen fuel cell, the electrode used is carbon electrode.Hydrogen is passed through through the anode compartment where it is oxidised. Oxygen is passed through the cathode compartment ...
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2answers
43 views

How to determine at which temperature does iron in stainless steel undergoes spontaneous oxidation?

It is my understanding that iron oxidation in stainless steel is prevented by adding chromium, which creates chromium oxides at the surface that shield the bulk of the material from further oxidation. ...
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How to determine symmetry of the system from the term symbol?

I'm studying term symbols. I can derive them mechanically from the electron configuration using the complete table of microstates. Let's consider a typical example - an atomic carbon with the ...
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2answers
123 views

Does chemical bonding decrease the entropy of the universe?

I have read in many credible texts ( including "a brief history of time" ) that nature always increases entropy, that is, the entropy in the universe increases. But I learnt that atoms and molecules ...
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1answer
18 views

Why enthalpy variation is not zero at a constant pressure physical state transformation?

I was checking Castellan's Physical Chemistry. So, there's a passage that states: Consider a liquid in equilibrium with its vapor under a pressure of 1 atm. The temperature is the equilibrium ...
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83 views

How exactly does quantum mechanics play a role in our day to day life?

From my understanding, quantum mechanics applies mainly to small microscopic particles. When it comes to macroscopic objects, the wave functions collapse and the quantum mechanical properties are lost....
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183 views

Why does the humidifier “really” make a stove's flame orange? [duplicate]

I answered this question- Why does the humidifier make a stove's flame orange? and earned 300 rep points for it as an "accepted" answer, but serious doubts have arisen about its correctness. ...