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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70 views

Relationship Atmospheric Gases and Ocean Gases [closed]

If this question is better suited for the Earth Science StackExchange or another StackExchange please let me know. Edit 1: Modified for clarity and brevity. Something that's unclear to me is the ...
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How to calculate the i-value of known NaCl solution, if it is isotonic with known solution of glucose?

How do I calculate the value of $i$ for 1.17% solution of $\ce{NaCl}$, if it is isotonic with 7.2% solution of glucose? I actually do not know where to start in this question. is it possible to ...
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1answer
176 views

Why is a TTT diagram called isothermal transformation diagram?

Why are TTT diagrams called isothermal temperature diagram?As far as I know the temperature variation is plotted with the variation of time in a TTT diagram. Then why do we call it "isothermal".What ...
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Temperature dependence of reaction rates

Is it correct to say that "Increasing the temperature will always increase the rate of any chemical reaction"? Many articles on the internet and textbooks say yes but what about biochemical reactions ...
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1answer
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How would I find the molarity/concentration of a gas using pV = nRT?

The problem I'm working on is: At $\pu{1100 K}$ and a total pressure of $\pu{1 atm}$, $\ce{SO3}$ is $75.0\%$ dissociated. $$\ce{2SO3(g) <=> 2SO2(g) + O2(g)}$$ Assume $\pu{1.00 mol}$...
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Finding the pH of the solution

In this video, at 3:30 min professor solves two equations $$\ce{H2O —> H+ + OH-}$$ and $$ \ce{HCl —> H+ + Cl-}$$ and deduces $[\ce{H+}] = [\ce{Cl-}] +[\ce{OH-}]$. How come this happen from ...
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1answer
60 views

Calculating bond energy given the enthalpy value of burning reaction

The burning enthalpy (exothermic) of $\ce{NO +O2 ->NO2}$ is $\pu{57 kJ mol^-1}$ and $\ce{O=O}$ bond energy is $\ce{494 kJ mol^{-1}}$, then what is the bond energy of $\ce{N-O}$ ? So I balanced the ...
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Explain why can't zinc be plated out from a Zn(II) solution using standard reduction potentials

I am currently learning about electrochemistry using Zumdahl's Chemistry [1, pp. 709–710]. One of the critical thinking questions is Why can $\ce{Zn}$ not be plated out from an aqueous solution of $...
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In which order should you prepare a microemulsion?

So I have isoooctane (oil phase) ,CTAB (surfactant) ,1-butanol (cosurfactant) , and an aqueous solution of metal nitrates as the water phase. In which order should i add these components? Or any ...
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How to calculate the internal energy change on a phase change?

Since, the system is in material equilibrium, dG for the system for the reaction is 0. However, our instructor told us that dA has a value. How is that?
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Diffusion between phases based on chemical potential

How is the concept of diagram(b) different from that of (e) and (d) from (f)?Someone told me in one of my earlier posts (Why will A atoms diffuse from β phase to α phase and B atoms from α phase to β ...
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Reaction of sulphur with calcium carbonate

Can sulphur react with calcium carbonate to form sulphur trioxide and calcium carbide, as the energy of 3(S=O) is greater than ((C=O) +2(C-O))? EDIT: i forgot to say that this is in an oxygen-free ...
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Why will A atoms diffuse from β phase to α phase and B atoms from α phase to β phase?

At the initial compositions 1 and 2 of $α$ and $β$ respectively the chemical potentials of A and B atoms in each phase can be found by extrapolation of the tangents to the free energy curves at 1 and ...
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1answer
96 views

How to calculate molecular emission spectra?

Is there free software which can calculate the fluorescence emission spectra of organic molecules? Let's say for example: rubrene There is a bunch of quantum free quantum chemistry software: https://...
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39 views

Conditional kinetic equations

From a biological system, I got the following reaction: $$A+B+D\rightarrow C+C_1D$$ ($C_1D$ is a certain complex) However, if at any given time there are no $D$s to react, and only then, instead the ...
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1answer
589 views

How is the 'rate law' and 'order' for the ozone decomposition reaction can be defined?

How is the 'rate law' and 'order' for the following reaction can be defined? $$\ce{2O3 -> 3O2}$$ "The expression that correlates the rate of reaction with concentration of reactants is known as ...
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1answer
105 views

What is the reason for phase separation? [closed]

I have seen phase separation as a phenomenon taking place. However I do not understand why this phenomenon occurs as a counter example to the natural laws of diffusion along the concentration gradient....
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Catalyzing the breakdown of Si-O bonds

What catalysts can catalyze the breakdown of (Si-O) bond ? Can you mention some books(ebooks or hard cover) or websites that cover a lot of information about (Si-O) bond characteristics? I have ...
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Finding EMF of a galvanic cell without standard potentials

For the galvanic cell $$\ce{Ag | AgCl(s), KCl (\pu{0.2 M}) || KBr (\pu{0.001 M}), AgBr(s) | Ag}$$ find the EMF generated given $K_\mathrm{sp}(\ce{AgCl}) = \pu{2.8e-10},$ $K_\mathrm{sp}(\ce{...
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1answer
203 views

Why enthalpy changes in phase transition when there is no change of temperature?

Why there is a change in enthalpy in phase transition? I'm asking because enthalpy depends only on temperature: $$\mathrm dH = C_p\,\mathrm dT,$$ and the change in temperature is $\mathrm dT = 0.$
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Gibbs free energy calculation for redox reaction

I was wondering if it is correct to calculate the Gibbs free energy of reaction at $P = \pu{1 atm}$ and $T = \pu{1100 K}$ using the NIST-JANAF thermochemical tables. For example, for the reaction of ...
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264 views

For a gas having molar mass M, express specific heat at constant pressure in terms of heat capacity ratio

For a gas having molar mass $M$, express specific heat at constant pressure in terms of heat capacity ratio. My attempt: using $ C_p - C_V = R $ and $ \dfrac{C_p}{C_V} = \gamma $ $ C_p = \dfrac{...
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Determine the velocity of the O fragment after the dissociation

A $\ce{SO3}$ molecule is radiated with light with a wavelength of $\pu{193 nm}$, which results in photodissociation. $\ce{SO3} + \text{photon}(\lambda=\pu{193nm})\ce{-> SO2 + O}$ It is ...
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1answer
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Why do we use Ḡ (“G bar”) as a notation for partial molar free energy?

For partial molar entropy there is a bar that is positioned above the $G$ with a subscript I that is sometimes added to the $G~(\bar{G}).$ The bar I read sometimes denote the "partial nature of the $G$...
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48 views

Is the rate of electrolysis the same throughout as long as voltage is same

In an electrolytic cell, where the electrolysis of dilute sulfuric acid is taking place, would the rate of electrolysis be constant always, even at the beginning? By rate of electrolysis, I mean the ...
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165 views

Calculating bond dissociation enthalpy of F-F bond

$$\ce{N2 + 3 F2 -> 2 NF3} \quad ΔH = \pu{-263 kJ mol-1}$$ The bond dissociation enthalpies of the nitrogen triple bond and nitrogen–flourine bond are $\pu{946 kJ mol-1}$ and $\pu{272 kJ mol-1}....
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Why is the y intercept of a G vs X curve treated as chemical potential?

Whenever I am to prove the fact that the $y$ intercept to the $G$ vs $X$ curve is basically my chemical potential, there are two equations that need to be assumed. One is $$G=\mu _{A}X_{A}+\mu _{B}X_{...
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2answers
109 views

Will mixing hydrogen and oxygen without a spark result in combustion? [duplicate]

I plan to do the electrolysis of dilute sulphuric acid. This will produce hydrogen gas and oxygen gas at the anodes. I do not plan to collect these gases, but to simply let it form and release into ...
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Zero-filling Fourier Transform in NMR [duplicate]

I understand zero-filling increases the resolution of an NMR signal in the frequency domain, but I fail to comprehend how. Why do the artifical points appear between the real points in the frequency ...
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1answer
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What is the cause of decrease in volume of gaseous mixture in the following problem? [closed]

I am studying Gaseous State. The problem says: A mixture of gas contains $\ce{N2}$ and $\ce{C2H2}$. $\pu{20 \\mL}$ of this mixture is added to $\pu{70\\mL}$ of $\ce{O2}$ and combustion is allowed to ...
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What happens when two galvanic cells are placed in series

I understand how a single galvanic cell works, and the relation of equilibrium and the Nernst equation. But this appears to contradict the higher voltage in a series configuration because it ...
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23 views

What is the equation that describes the variation in concentration of an inhibitor in an heterogeneous catalysis?

I find myself in quite a pinch: I have to sustain a Chemical Physics exam, and I know for a fact that the professor often asks this particular question: Suppose that we have both a reacting species ...
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271 views

Why is the equilibrium constant unitless?

I read that the equilibrium constant is unitless because the molar activities of each of the species are used in the equilibrium expression, not the actual concentrations themselves. I understand that....
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1answer
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How to explain Gibbs free energy is a pressure-dependent state function?

I'm aware that through deriving Gibbs free energy to infinitesimal changes, we could get the formula: $\mathrm dG = V\,\mathrm dp - S\,\mathrm dT$, giving that Gibbs free energy is pressure-dependent. ...
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Arrhenius equation using concentration

I've been conducting some experiments to determine the temperature dependence of a reaction. To do this, I've been conducting the experiments at different temperatures and generated a graph of $\ln{[\...
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1answer
42 views

Is there any book where specific heat capacities are given?

I want to find the value of the specific heat capacity of aluminium nitrate nonahydrate, in order to calculate mixing effects in a chemical reaction. I am looking for a source, such as a book or link ...
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Are there any gases that can not be turned into liquid, or liquids that can not be frozen solid?

My son points out that some solids can not be melted (because they combust, for example). He wonders if there are any liquids that can not be frozen, or gases that can not be liquified.
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1answer
333 views

Conductance of the mixture of two solutions with given resistance values [duplicate]

If $R_1$ and $R_2$ are the resistances of two solutions of equal volume what is the conductance of the mixture in the same conductivity cell? In general, I grasped neither the approach, nor the ...
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How to calculate the value of heat absorption/ heat release during water electrolysis?

The overall reactions with the enthalpies of water electrolysis at room temperature can be represented by the equation below: $$\ce{2H2O + \pu{237.2 kJ mol-1} + \pu{48.6 kJ mol-1} → 2 H2 + O2}$$ ...
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Exothermic: enthalpy or heat?

I am used to thinking of exothermic reactions as being defined as having negative $ΔH.$ However, I also am used to hearing/thinking of exothermic reactions as "releasing heat". Since change in ...
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1answer
108 views

Why does Freundlich adsorption isotherm not have a term for surface area?

Why does Freundlich adsorption isotherm not have a term for surface area? The formula given by Freundlich adsorption isotherm: $$ \frac{x}{m}= k P ^{1/n}$$ Where $x$ is the mass of gas adsorbed ...
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1answer
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What drives vibrational cooling in an excited stated?

As we excite a molecule from its ground state, $S_{0,v=0}$, to some excited state in a higher vibrational state, i.e. $S_{1,v'=3}$, what drives vibrational cooling within that excited state manifold (...
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Why doesn't beryllium, an elemental solid, obey Dulong and Petit's law?

Beryllium has a molar heat capacity of $\pu{17.7 J mol-1 K-1},$ which is quite far from the $\pu{25 J mol-1 K-1}$ as predicted by Dulong and Petit's law. What is the reason for this discrepancy?
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Calculate change in entropy when both temperature and volume change

Calculate the change in entropy when $\pu{23.5 g}$ of oxygen gas is heated from $\pu{240 K}$ to $\pu{360 K}$ in such a way that its pressure increases from $\pu{2.00 kPa}$ to $\pu{8.00 kPa}.$ Assume ...
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Why is there a z² label for d orbitals, but no x² and y² labels with corresponding shapes?

I know that the $\mathrm{d}_{z^2}$ orbitals are named as a result from the conversion of the angular component of the hydrogen-like wave function in terms of Cartesian coordinates, but how come we ...
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Changing conditions of gaseous mixture

A gaseous mixture of $\ce{NO2}$ and $\ce{N2O4}$ is sealed in 4 identical vessels with movable pistons. When the conditions are modified as described in 1) to 4), in which condition does the molar ...
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4answers
253 views

Relation between activation energy and rate constant

Consider two types of reaction. One has more activation than other. If we increasing temperature by same amount in both, rate constant of which reaction will increase more? My attempt: as we know ...
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1answer
322 views

Entropy change in non-ideal solutions

We know that some solutions show positive deviations and some show negative deviation from Raoult's law.The former is endothermic and the latter is exothermic. And again, the volume change show ...
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507 views

Which of the following statements is true if HI is formed in the following reaction?

Which of the following statements is true if HI is formed in the following reaction? $$\ce{H2(g) + I2(g) -> 2HI(g)}$$ a. There are no collisions between the reactants in the reaction. ...
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Why electrons move to Cu in galvanic cells?

I'm student who learning about chemistry, and I got problem about understanding why electorns move to Cu in galvanic cells. Let's think the reason for electrons going to Cu is that the standard ...

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