Questions tagged [physical-chemistry]

The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.

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Is the phase of an electron quantized?

Trying to conceptualize bonding and antibonding orbitals from a quantum mechanics perspective. So the energy of an electron is quantized, therefore, the frequency is quantized from the equation E=hf, ...
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The role of carbon dioxide in temperature regulation? [closed]

Common concept 1) is that human body cells turns sugar into energy via combustion, using oxygen and releasing heat, carbon dioxide and water. Common concept 2) is that both oxygen and carbon dioxide ...
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Temperature change in reversible and irreversible adiabatic processes

An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system. If Ti is the initial temperature and Tf is the final temperature, then which is greater (Tf)rev Or (Tf)irr? As ...
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Why is the value of the heat capacity ratio γ the same for molecules with the same atomicity?

The heat capacity ratio is defined as the ratio of the heat capacities at constant pressure and volume respectively: $$\gamma = \frac {C_p}{C_V}\tag{1}$$ Then obviously $$\gamma = \frac{n\,C_p\,\Delta ...
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Why is my battery of galvanic cells not enough to power a lamp rated for a lower voltage than the battery provides?

I made a series of 12 galvanic cells with saltwater as an electrolyte and zinc and copper as electrodes. It produces 8.8 V, but it can't even light a 2.5 V bulb. Please assist in understanding what ...
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Gibbs free energy for an irreversible process

In an irreversible process taking place at constant T and P in which only pressure-volume work is being done, the change in Gibbs free energy (dG) and change in entropy (dS) are? The answer to this ...
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How should I evaluate $\left(\frac{\partial U}{\partial V}\right)_T$ with van der waals equation: $P = \frac{nRT}{V-nb}-a(\frac{n}{V})^2$?

So in my homework I was able to get this- $\left(\frac{\partial U}{\partial V}\right)_T = T(\frac{\partial P}{\partial T})_V - P$ but now I'm trying to plug in $P = \frac{nRT}{V-nb}-a(\frac{n}{V})^2$ ...
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Why does the equation for chemical potential apply to liquids and aqueous solutes?

The equation for chemical potential of a gas can be derived as such: At constant temperature, $$\mathrm dG = V\,\mathrm dP \label{eqn:1}\tag{1}$$ Substituting with the ideal gas law $PV = nRT$, $$\...
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Why does band heads arise in vibrational-rotational spectra?

I learn that a band head is a region of maximum intensity due to many lines falling together. It can be determined by differentiating the expression for the R branch. To no avail, I cannot find any ...
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Cubic nature of van der Waals' gas equation

$V_m^3-\dfrac{RT+bP}{P}V_m^2+\dfrac{a}{P}V_m-\dfrac{ab}{P}=0$ So, At $T<T_c$ the above equation has three real roots say $V_1,V_2,V_3$, my doubt is what does this mean physically because for some ...
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Understanding the molar free energy to simulate phase separations (Na2O-SiO2)

I am a mathematician and I want to understand the molar free energy model given in Kim and Sanders (2020) Equation (1), that is, \begin{equation} f(c,T) = RT \big(c \log(c) + (1-c) \log(1-c)\big) + \...
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thermodynamic equilibrium

A thermodymic system is said to be in equilibrium if it satisfies the two conditions : 1-The system’s macroscopic properties remain constant with time. 2-removal of the system from contact with its ...
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Calculating Coordination Number in Solid State [closed]

i)For c.n of a cation can we consider another cation as the nearest ion(in c.n) suppose it is nearer than the anion? ii)For finding c.n of tetrahedral voids the distance from the tetrahedral void to ...
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Why probability for an atom is fraction for population?

In the canonical ensemble the probability of finding an atom (or molecule) in its $i$-th energy state is given by the Boltzmann factor. This probability is interpreted as the number of microstates ...
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How do I find conversions for a reaction with phosphoric acid? [closed]

I have a solid ash mix containing oxides(ZnO, NiO, MgO, Cr2O3, etc.) and salts (Na2SO4, K2SO4, apatite, etc.). My teacher asked me to write all of the reactions with phosphoric acid (should be between ...
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Reason behind colour change of indicators [duplicate]

We know that for testing acids and bases we use the indicators. For eg. Acid turns blue litmus red and base has no effect on the blue litmus. Similarly colours are also seen in phenolphthalein, methyl ...
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Table of viscosity of water vs temperature

Above is the table for water physical properties table with temperature related with a,v,b,Pr,Ra factor. This table has temperature only from 0 to 100. May I ask if there is a full table for this with ...
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Calculating zero-point energy for the Varshini potential

As per my understanding, for a harmonic oscillator, we can find the zero-point energy by the relation below: $$ E_0 = \left(0 + \frac{1}{2}\right)\hbar \omega$$ The equation for the potential in ...
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How does the enthalpy change of bond enthalpy relate to enthalpy changes of formation? What's the difference? [duplicate]

The enthalpy change = sum of bond energies broken (reactants) - sum of bond energies made (products). Then I read The enthalpy change = sum of the enthalpy change of formation of products - sum of the ...
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Is there an agreement for a specific temperature referred to in the context of standard Gibbs energy? [duplicate]

I found an exercise in Physical Chemistry by Atkins et al, 8th edition, page 235 that I found confusing. The question is as follows. "7.2(b) Molecular bromine is 24 per cent dissociated at 1600 K ...
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Can sodium sulfate be used in the salt bridge?

My book mentions sodium sulfate ($\ce{Na2SO4}$) as an electrolyte that can be used in a salt bridge. I'm asking this question because ChemLibreTexts says that It is also important that the charge ...
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Why should the cubic equation in volume, obtained from Van Der Waals equation of state, have equal roots at the critical point?

The video Edmerls — Derive Equation for Critical Constants in terms of Vander Waal's Constants. | Physical Chemistry (YouTube) provides a derivation of the relationship between the van der Waals ...
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Electrode potential for saturated silver carbonate solution

An electrochemical cell is set up to measure the electrode potential $E(\ce{Ag^+}/\ce{Ag})$ using the saturated $\ce{Ag2CO3(aq)}$ solution $(K_\mathrm{sp}(\ce{Ag2CO3(aq)},\pu{25 °C}) = \pu{6.3E-12})$ ...
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Why is octasulfur present in equation for standard enthalpy of formation of sulfuric acid?

Write a balanced chemical equation corresponding to the standard enthalpy of formation of $\ce{H2SO4}.$ \eqref{rxn:r1} is the given answer, \eqref{rxn:r2} is my answer: \begin{align} \ce{1/8 S8 (s) + ...
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derivation of activity coefficient from Margules laws?

basics In Margules activity model, the excess Gibbs free energy is expressed as: $$ \frac{G^{ex}}{RT}=X_1 X_2 (A_{21} X_1 +A_{12} X_2) + X_1^2 X_2^2 (B_{21}X_1+ B_{12} X_2) + ... $$ meanwhile, we ...
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According to Maxwell-Boltzmann distribution, what is probability distribution function proportional to?

If, according to the Maxwell-Boltzmann distribution $${f(v)}\propto\exp\left(-\frac{\varepsilon}{kT}\right),\tag{1}$$ which is the equation from which the whole final equation is derived, then why is ...
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Is haloform reaction considered to be disproportionation? [duplicate]

A question in an exam listed a number of compounds and the task was to find the number of compounds which will undergo disproportionation in conc. $\ce{NaOH}$. One of the compounds was $\ce{CCl3CHO}$, ...
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What is the paramagnetic susceptibility of sodium at around room temperature?

Proposed solution: This question comes from Tanner's manual Introduction to the Physics of Electrons in Solids, at the chapter dedicated to the application of the Fermi gas model. The Fermi energy is $...
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Shielding vs electron-electron repulsion

Example of shielding: (source) The last electron in the 6s subshell of $\ce {Cs}$ is shielded from the nucleus by the inner electrons. Example of electron-electron repulsion: The electron affinity of ...
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4 votes
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Spontaneous reaction between chlorine and a hypothetical atom

Suppose, my hypothetical element is $\ce X$, whose first ionization energy is $\pu{200kJ/mol}$. An atom of this element will react with an atom of chlorine (assume that I've already dissociated a ...
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Liquid water barrier and water vapor permeable membrane sheets

I am running an experiment where I am trying to maintain the relative humidity of a thermally insulated chamber. I am successfully able to hold the humidity using different salt solutions (NACL-75% RH,...
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Is collision theory applicable only for molecules?

$$\ce{Na (s) + Cl_2 (g)->NaCl(s)}$$ Is collision theory applicable for the above reaction, or is collision theory applicable only for molecules? In other words, do chlorine atoms collide with ...
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2 votes
1 answer
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My book's claim about the shielding effect of s,p,d and f electrons

It's a relatively unknown Bangladeshi book. It's called "Chemistry-First Paper (Class XI-XII)" by Professor Haradhan Nag According to my book, "Electrons of s and p orbitals produce ...
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What happens during a displacement reaction? [closed]

When Zn metal is added to a solution of Cu(II)SO4, Zinc displaces Cu to form ZnSO4 as Zn is more reactive than Cu. What I don't understand is how. 1- What I'm assuming is: Zn metal collides with [SO4]...
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How to calculate rate of carbon dioxide from rate equation? [closed]

The concentration of carbon dioxide that changes with time: $$\ce{CO2(g) + H2O(l) <=>[$k_\mathrm{fwd}$][$k_\mathrm{rev}$] HCO3-(aq) + H+(aq)}$$ How to calculate the integral for the following ...
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4 votes
1 answer
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pKa of methylene protons in cycloheptatriene vs cyclopropene

The $\mathrm{p}K_\mathrm{a}$ values of methylene protons in cycloheptatriene vs cyclopropene are found to be 60 and 36, respectively. From what I understand - both conjugate bases are non-aromatic (...
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Can there be a molecule where every atom is covalently bonded to every other atom? [closed]

I was wondering if muliple atoms could bond in a ring, but share a pair of electrons with every other atom in the molecule so that every atom is connected to every other atom. Would it be possible for ...
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Example of reactions series A → B followed by A + B → 2 C

I'm currently writing about geometric numerical integration and I need an example of the following series of chemical reactions: \begin{align} \ce{A &->[$k_1$] B} \tag{R1} \\ \ce{A + B &...
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Dissolution Thermodynamics - What is the standard state in units of mole fraction?

I have recently been working on a project that involves the correlation of mole fraction solubility using the Apelblat equation (in simplified form: $\ln\chi = A +\frac{B}{T}$), which can allegedly be ...
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Work done by gases on each other in the process of mixing them

I was wondering if gases, which are in the process of mixing, do any work on each other. I haven’t found many resources on this. We all know that gases, which have a higher pressure than their ...
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Diffusion of particles across a plane surface

A relatively viscous material is coated with a thin film consisting of gold nanoparticles that can diffuse into the material. We can assume that all particles have a diameter of $\pu{25 nm}.$ Coating ...
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Explaining the process of boiling a liquid

as of right now, I am confused by the thermodynamic definition of boiling. It is stated that boiling occurs when the vapor pressure of a liquid is the same as the ambient atmosphere. Now suppose we ...
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Products formed on the reduction of KMnO4 in aqueous solution

The Latimer diagram for $\ce{MnO^-_4}$ is given below: $$ \ce{MnO^{-}_4 ->[0.56V] MnO^{2-}_4 ->[2.26V] MnO_2 ->[0.95V] Mn^{3+} ->[1.51V] Mn^{2+} ->[-1.18V] Mn}$$ Then I have calculated ...
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Why doesn’t ferrous sulfate appear orange in vinegar?

When I mix ferrous sulfate crystals with water, the solution almost immediately turns orange. However, when I mix ferrous sulfate with vinegar, it doesn’t change colors. Why is this?
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Why can't all chemist/IUPAC agree to make equilibrium constant as dimensionless?

I mean the gold book defines two terms as the equilibrium constant - the standard/thermodynamic equilibrium constant and generic equilibrium constant. To me, only the thermodynamic one seems correct ...
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Is there a recommended frequency when driving an alkaline water electrolyzer?

We are designing a small electrolyzer (about 1 kW input power) for HHO gas generation. Sadly most of the literature online is bordering on the snake oil… However, it works fine with DC driving. Now ...
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Why is the value of $A$, in the expression for Boltzmann's distribution of speeds, not directly calculated?

I've read the proof for the expression for Boltzmann's distribution of speeds on this site. There, $f(v)$ is first factorized into $f(v_x)$, $f(v_y)$ and $f(v_z)$ and $A$ into $A_x$, $A_y$ and $A_z$. ...
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Products formed on the electrolysis of wet HF

We know that, electroysis of water produces $\ce{O2}$ at anode and $\ce{H2}$ at cathode. In a similar way I thought that on electroysis of $\ce{HF}$ it would produce $\ce{F2}$ and $\ce{H2}$ at their ...
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How to calculate the temperature of a mix?

I'm trying to solve a problem but there is something im not quite getting. It says, if we mix 84.2 mL liquid water at a 15°C and 50 mL of 100% sulfuric acid at 25°C, What is the maximum temperature ...
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How can the reaction heat be ignored in an energy balance?

I have received from my professor the following (here summarized) problem: A first-order exothermic reaction A->B takes place in a tubular reactor (typical PFR). The tube is cooled to a constant ...
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