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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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Bond Nature of a comound [on hold]

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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2answers
29 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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2answers
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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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How much does steam expand in relation to its temperature (assuming starting at 100 °C) and constant pressure in a flexible container? Thanks! [on hold]

How much does steam expand in relation to its temperature (assuming starting at 100 °C) and constant pressure in a flexible container? For example, if 1 L of $\ce{H2O}$ expands to about 1600× the ...
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2answers
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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
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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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19 views

Why concentration of water is not taken 1 for the equilibrium constant of esterification reaction? [on hold]

For pure liquids and pure gases, we approximate the concentrations equal to 1. In case of the esterification reaction, why do we write $\ce{H2O(l)}$ in the $K_\mathrm{c}$ formula since we have ...
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Schrodinger Equation : TDSE and TISE [on hold]

How can one particular Schrodinger equation be both time-dependent and time-independent at the same time? I mean its wrong by the very notion to say both simultaneously. We encounter many instances ...
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Can you please tell me the process? [on hold]

The value of Kc=4.24 at 800K for the reaction, CO(g)+ H20(g) >CO2(g) + H2(g) Calculate the equilibrium concentrations of CO2, H2, CO and H2O at 800K, if only CO and H2O are present initially at ...
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1answer
26 views

Pls help confusing [on hold]

Its a chemical kinetics quedtion from jee main 2019 i got answer 10 but many places answer is 5 i thought that as reaction is first order it must be equal to half life
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To find out how much urea will separate out? [on hold]

I know how to solve the above question I will let water used be 'w' gm and then will apply the formula of decrease in free zing point and then calculate 'w' then it would be subtracted from 250 gm . ...
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what is the difference between oxidation state, charge and valency? [duplicate]

Is there any specific atom or compound or molecule possessing oxidation state different from charge and valency, so that we can clearly understand the difference between the three.
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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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0answers
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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
34 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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44 views

heat produced to make Fe

For production of pure iron from $\ce{Fe2O3}$, a factory is mixing carbon monoxide with this iron oxide. Given the information below and assuming the yield 100%, how many kilowatt hours would be ...
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1answer
29 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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0answers
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How to calculate pollutant mass concentration in exhaust air?

I want to calculate the mass concentration of methane in exhaust air as unit gram per cubic meter per hour. Assumed we have the following situation: A bioreactor ...
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1answer
36 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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1answer
50 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
27 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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Why do some cations and anions interact with water to form corrresponding acids and bases(hydrolysis)? [duplicate]

I have seen in my textbook that on cations/anions formed on ionization of salts either exist as hydrated salts in aqueous solutions or interact with water to reform corresponding acids/bases depending ...
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1answer
66 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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0answers
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Can someone explain, how to complete the missing data in this table? [closed]

I am learning kinetics in chemistry, and so far I understand it. This problem is from physical chemistry and I am using a textbook called thermodynamics. When it comes to this problem I don't even ...
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1answer
39 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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2answers
37 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
50 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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0answers
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nanostructured microspheres! are they in the nano or micro scale [on hold]

I can read some articles with TEM images that show particle sizes of more than 200-500 nm, while in the same papers it is mentioned these are nanostructured microspheres and it is also mentioned the ...
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2answers
47 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
22 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
44 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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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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Entropy change between between temperatures? [duplicate]

My chemistry textbook mentions the formula for change in entropy as $$\Delta S= \dfrac{\Delta q_{rev}}{T}$$ It then tells me that to calculate ΔS for a change between two temperatures, one would sum ...
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2answers
38 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
128 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
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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
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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
42 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
45 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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1answer
37 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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0answers
34 views

Entropy of lead storage cell

I am having trouble with calculating the entropy of a lead storage cell. The standard cell potential is given as $\pu{2 V}$ and the standard enthalpy change is $\pu{-306 kJ}$. I found out the Gibbs ...
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1answer
43 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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2answers
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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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1answer
110 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
35 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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0answers
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Calculating pH of extremely dilute HCl solution [duplicate]

The $pH$ of a $10^{-8} M$ (M = moles per liter) $HCl$ solution is to be calculated. The plan is to calculate the ionization constant ($K_a$/acidity) first, and then derive the $pH$. However, as the ...
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0answers
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How to get polyethylene isophthalate pellets from pellet form into a cast film?

For some research I'm doing, I need to form a cast film from pellets of polyethylene isophthalate. I'm unable to find a listed melt temperature of PEI, although as this is an isomer of PET, I can ...
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0answers
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How do buffer solutions work? [duplicate]

I can't understand how buffer solutions resist the change in pH.Addition of strong acid in an acidic buffer results in its dissociation and production of hydrogen ions and these H ions react with ...
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1answer
51 views