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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 equation below for Gibbs energy only applicable under standard conditions?

This is quite confusing to me because it seems as if a lot of people use standard state equations and non standard state ones interchangeably: $$ΔG^\circ = -nFE^\circ$$
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1answer
36 views

What happens to depression when two solutions are mixed? [closed]

Equal volumes of $\pu{1.0 M}$ $\ce{KCl (aq)}$ and $\pu{1.0 M}$ $\ce{AgNO3 (aq)}$ solutions are mixed. The depression of freezing point of the resulting solution (with respect to water) will be (assume ...
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45 views

Solid state and Bragg's Equation

A frst order reflection from (111) plane is observed for LiX with 2theta =24.6 degree (X-ray of wavelength 1.54 angstrom). Assuming LiX to be a cubic crystal system, calculate the length of the side ...
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75 views

dSsur, dS and dStotal relation

By definition, dS=dqrev/T. Based on my understanding, the subscript rev means that the dq is heat exchanged in a reversible pathway from a state i to another state f, regardless of the actual ...
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58 views

Model of an ideal liquid in chemistry

In chemistry there are ideal models/concepts of ideal crystal, ideal gas and even ideal solution, but there is no model/concept of ideal liquid. In physics (fluid dynamics, to be precise) there is a ...
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1answer
41 views

Compound having highest standard reduction potential

Which compound has highest SRP (standard reduction potential) value, e.g. the strongest oxidising agent? In most tables $\ce{F2}$ is at top with $E^\circ = \pu{2.87 V}$, but I've found a table listing ...
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24 views

Deriving the entropy as a function of concentration

In a physical chemistry class, the professor derived entropy $S$ as a function of concentration starting from $S=k\ln(W)$. Somehow he made a mistake and ended up with the wrong sign. This remains ...
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37 views

what is the exact meaning of oxidation state? [duplicate]

can you mention the concept of oxidation state without its simple definition i-e it is the apparent charge +ve or -ve.....😪 I found these in wikipedia but didn't understand."Conceptually, the ...
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85 views

Why does bond breaking in ATP release energy? [duplicate]

We always come across that formation of bonds releases energy, and bond breaking requires energy, but in the case where ATP converts into ADP or AMP (bond breaking), energy is released. Why? Further, ...
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59 views

Why enthalpy is defined at a constant pressure?

How absolute enthalpy and enthalpy change are defined? What is the clear difference between enthalpy and heat? Is it the constancy of pressure what makes the enthalpy a state function? My teacher ...
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1answer
104 views

adiabatic expansion vs Joule-Thomson Effect

Source: The1stLawofThermodynamicsLesson4 I am looking for difference between adiabatic expansion and Joule-Thomson effect. Looking at the setup demonstrating Joule-Thomson effect, I find no essential ...
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16 views

In dS≥dQ/T, material equilibrium means that there is not material changes at all or that a material change can be reversible and at equilibrium?

I am reading Levine's Physical Chemistry, I know how to arrive to that equation, but I have questions. First, $\mathrm{d}S=\mathrm{d}Q/T$ for material equilibrium, but if there is a heat flow I ...
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20 views

How do I make a 0.5 M citrate buffer at pH 4.5?

I need to make a citrate-sodium citrate buffer at 0.5 M concentration and pH 4.5. I calculated the molarities of the citrate and disodium citrate based on the Henderson Hasselbalch equation, using a ...
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1answer
37 views

How to specify atomic carbon terms in the coupled and uncoupled representation?

So, we know, that the atomic carbon in the electronic configuration $1s^22s^22p^2$ has the following terms $${}^1S, {}^1D, {}^3P$$ My question is - how can I correctly specify these terms in the ...
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1answer
53 views

Why is excluded volume in van der Waals equation divided by 2?

Source: Physics Stack Exchange The excluded volume calculated based on the diagram is 8 times the volume of a molecule. The volume is then divided by 2 to give the so-called excluded volume per ...
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130 views

Compressibility Factor Graph - Which gas attains a deeper minimum?

As in the given graph, how do I predict which curve among that of hydrogen, methane, and carbon dioxide attains a deeper absolute minimum? (greater deviation from Z=1). In fact, how do I make this ...
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54 views

How is a NMR spectrum obtained?

I am reading about NMR, and from what I'm understanding it should give information on the transition energies in the spectrum of the nuclear spin in a magnetic field. What I don't understand is how ...
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1answer
28 views

Difference between adiabatic and nonadiabatic tunneling for molecule

What is the difference between adiabatic and nonadiabatic tunneling for a molecule in a laser-field? Does nonadiabatic tunneling necessarily relate to the Conical intersection or curve-crossing?
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68 views

What is the radius of the atoms? [closed]

In a recipient there is an unknown monoatomic gas that occupies a volume of $\pu{230 cm3}$, at $\pu{300 K}$ and $\pu{1 atm}$. It is known that the atoms occupy a volume of $2\times10^{-4}$. Find the ...
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1answer
48 views

What are good examples of questions that make college students think about chemistry concepts? [closed]

I am teaching the second semester of general chemistry at the college level. The course tends to get bogged down in calculations, and sometimes we forget about the big picture and what is going on at ...
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44 views

Intuitive explanation for depression of freezing point

Why does depression of freezing point takes place if a non-volatile solute is added to the solution? For more details about the question checkout this link below Depression of freezing point
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2answers
60 views

Why are reversible reactions spontaneous?

If a reversible chemical reaction is spontaneous in one direction, shouldn't it be non spontaneous $(ΔG > 0)$ in the other? In other words for the reaction: $$\ce{A + B ⇌ C + D}$$ if $$\ce{A + B ...
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57 views

Exact meaning of constant volume heat capacity

From Wikipedia: $$ \left(\frac{\partial U}{\partial T}\right)_V = \left(\frac{\partial Q}{\partial T}\right)_V = C_V, $$ $C_V$ is what known to be constant volume heat capacity. I don't really get ...
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1answer
28 views

Standard electrode potential

What is meant by the following: Electrode potential for $\ce{M^3+/M}$ Is it standard oxidation potential (SOP) or reduction potential (SRP)? What does a high positive or negative value for SRP and ...
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1answer
65 views

Is delta S the same in reversible and irreversible processes?

I've read that change in entropy of a system is the same for a system in reversible and irreversible processes since it is a state function and does not depend on the pathway. Does this only apply to ...
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44 views

First Order Chemical Kinetics

I have the following system of reactions: \begin{align} M & \xrightarrow{\lambda(M,W)}M+M \\ W & \xrightarrow{\lambda(M,W)}W+W \\ M & \xrightarrow{\mu} \emptyset \\ W & \xrightarrow{\...
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45 views

Is the adsorption of dissolved iodine onto activated carbon physical adsorption or chemical adsorption?

For an experiment, I am looking to see the effect of temperatures from 0–100 °C on the efficacy of activated carbon as an adsorbent. My adsorbate is iodine and I am confused as to whether the ...
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4answers
143 views

Changes in pressure for an equilibrium reaction containing a solid/liquid on one side only

For a reaction where there is only one solid/liquid present, but gases present as both reactants and products (are there any examples of this type of reaction?): $$\ce{A(s) + B(g) <=> C(g)},$$ ...
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3answers
287 views

What are the units of Kc and Kp?

They are both equilibrium constants as far as I know. Kc is in terms of molarity and Kp is in terms of pressure. Also both of them are ratios of respective quantities [ ratio of molarity(s) in Kc and ...
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2answers
32 views

How does the process of nucleation work for boiling liquids?

I have a somewhat clear picture how (on the molecular level) a gas turns into a liquids as it cools. When a gas has a certain temperature, its molecules on average have a high enough kinetic energy so ...
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1answer
44 views

Why do power requirement figures for water electrolysis on the web seem to be wrong?

I need to calculate the power needed to electrolyse 1 mole of water for a project. We will either use Polymer Electrolyte Membrane Electrolysis or Alkaline Water Electrolysis, they operate on 1.75V-2....
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1answer
51 views

Equilibrium constant from mole ratio

Chapter 4, problem 13 from the Chemical Priciples [1, p. 170]: Equilibrium concentrations Experiments have shown that at $\pu{60 °C}$ and $\pu{1 atm}$ total pressure, the equilibrium ratio of $...
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38 views

Equilibrium :. Why does a system at equilibrium try to undo the effect of external stress applied on it? [duplicate]

" Le Chatelier principle states that a system at equilibrium when subjected to external stress tries to undo the effect of that stress" In short, why does system at equilibrium follow Le Chatelier ...
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1answer
49 views

How hydrogen molecule is formed? [closed]

How two hydrogen atoms come close to form a bond ? Textbooks refer to a potential energy diagram but what i cant understand is what is this potential energy if the atoms are neutral . How they come ...
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1answer
132 views

Doesn't Ostwald's law of dilution contradict Le Chatelier's principle?

By Le Chatelier's principle, increasing the concentration of a weak electrolyte brings out more ions. By Ostwald's dilution law, increasing the concentration of a weak electrolyte brings out less ...
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171 views

What is the exact definition of the radial distribution function?

I have been very confused by the radial distribution function which is often used in chemistry to predict the probability of finding an electron at a distance from the nucleus. From Atkins' Physical ...
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1answer
37 views

what orbitals shape when we draw they together?(how do you shape orbitals together?) [closed]

If we want to draw all the orbitals of an atom, for example the atom of krypton, how will the space form of orbitals be when they are drawn together? in all scientific books,s,p,d and f orbitals shape ...
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48 views

Topic in Salt hydrolysis that I couldn't understand

Salts can be made up of all combination S of ( SA ,WA) and (SB , WB) I understand how to deal with salts of strong acids with both strong and weak bases and also of strong bases with weak and strong ...
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115 views

Reversible and irreversible cyclic processes

The answer in Arihant's book is given as (b), but wouldn't (c) be correct as well? This is a question of IIT JAM Chemistry. A system undergoes two cyclic processes 1 and 2. Process 1 is reversible ...
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66 views

Thermodynamics of a spontaneous isothermal chemical reaction. [duplicate]

Which of the following is/are correct for spontaneous isothermal chemical reaction? (A) $\Delta H = 0$, because $\Delta T = 0$ (B) $\Delta S = 0$ (C) $\Delta U = 0$, because $\Delta ...
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1answer
49 views

In zero order why we don't need the coefficient of reactant in integration of rate law?

For a reaction: $\ce{aA->product}$ The rate law is $\text{Rate}=-\dfrac{\mathrm d[A]}{a\,\mathrm dt} = k$ Where: $k$ is the rate constant $[\ce{A}]$ is the concentration of the reactant $\ce{A}$...
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1answer
25 views

Work function vs ionization enthalpy [closed]

I've seen that the work function of a particular metal is always greater than its work function. Is it the case always? If so why? For example, the first ionization energy of sodium is 5.14 eV/atom(...
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46 views

Does “higher symmetry” mean any symmetry group of higher order?

What is the precise definition of a higher symmetry in group theory? I see this term scattered around, such as in Cotton's Chemical Applications of Group Theory: ...In the cyclic groups each of the ...
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1answer
113 views

Using thermodynamics to predict the acid-base character of fluoride ion in water

I was working through the end-of-chapter exercises of the acid-base chapter in Shriver's Inorganic Chemistry when I came across the following problem: 4.7. The effective proton affinity $\ce{A^{'}_{...
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Why has na 1S0 term Ag symmetry?

This question is a continuation of Molpro - Connection between atomic term symbols and system symmetry. In the Feodoran's answer I found it somehow confusing, that ${}^1S_0$ term should be totally ...
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48 views

Finding the weighted parameters of the vertex adjacency matrix for a derivative of azulene

In my last question ( Numbering in a derivative of azulene ), I asked about the numbered of a molecule in order to find the Vertex Adjacency Matrix (VAM) of the same molecule. To explain my question ...
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79 views

Molpro - Connection between atomic term symbols and system symmetry

Let's say I have a carbon atom with the electron configuration $1s^22s^22p^2$. We know, that using atomic term symbols we can describe the following states: $${}^3P_0, {}^3P_1, {}^3P_2, {}^1D_2, {}^...
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Connection of term symbols with specific microstates for atomic carbon

I'm currently studying atomic term symbols. I wanted to try it on a simple atomic carbon with the electron configuration $1s^22s^22p^2$. I know, that only open-shell electrons are involved in the ...
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How are second and third electron affinities of atoms measured?

Wikipedia data page on electron affinities shows second and third electron affinities. Of course, they are negative, because one tries to attach electron to anion. But how are they measured or ...