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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17 views

calculate the number of phases and components [closed]

Calculate the number of phases and components in the following systems: i). Dilute aqueous solution of H2SO4 ii). Saturated solution of ...
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1answer
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On mechanism behind Marcus theory

Regarding the mechanism behind Marcus theory, I was wondering if reaction occurs through tunneling when it does not have sufficient activation energy? Wouldn't expecting reactions to occur this way be ...
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Moller Plesset Theory- MP2 correction [closed]

I have a molecule LiBH2 with C2V point group. I used 3-21G basis set and obtained RHF coefficients and symmetry of orbitals. I wish to find the set of orbitals (a,b,i,j)( where a and b are occupied ...
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67 views

Why does a first order reaction only depend on the concentration of a single reactant?

I am new to kinetics so please explain it from basic, If there is a reaction - $$\ce{A + B + C -> D}$$ In first order reaction rate is given by- $\mathrm R = k[\mathrm A]$ or $\mathrm R = k[\...
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Diethyl ether vapor pressure [closed]

Diethyl ether is a highly flammable and flammable organic liquid and is often used as a solvent. The vapor pressure of diethyl ether at 18 °C is 401 mmHg. What is the vapor pressure of diethyl ether ...
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Proof of law of gram equivalence [closed]

I m bit confused in this topic. Whenever i try to read this i get confused in some part or other. Can someone please help me out.. please tell me what is the proof of the law of gram equivalence. It ...
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1answer
41 views

Which of the following would be an example of something that is quantized? [closed]

How do we defind quantized there, why it is climbing a flight of stairs? Thank you!
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Does the same w/w percentage of all components in two solutions imply the same v/v or w/v percentage of all components in the two solutions? [closed]

Sorry for the heavy wording... Consider two solutions A and B. All components in A have the same mass percentage as that in B. Will all components in A also have the same volume percentage as that of ...
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25 views

Which is more stable and why: a half-filled s subshell or a half-filled p subshell? [closed]

Is $\mathrm{(1s)^2 (2s)^2 (2p)^6 (3s)^1}$ or $\mathrm{(1s)^2 (2s)^2 (2p)^3}$ more stable? Which has larger ionization enthalpy?
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1answer
38 views

What is the difference between primitive Hexagonal unit cell and Hexagonal closed packing HCP [duplicate]

There are 14 types of Bravais crystal lattices (Primitive + Centered) in 3D. Every solid in this universe is made by the unit cells of these lattices. With the help of these Bravais lattice can ...
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1answer
35 views

Using Equilibrium Constant [closed]

For the reaction, $$\ce{Fe^{2+}(aq) + Ag+(aq) <=> Fe^{3+}(aq) + Ag(s)}$$ $𝐾_\mathrm{𝖼}=\pu{1.17 dm^3mol^{−1}}$ $𝐾_\mathrm{𝖼}=\pu{1.17 mol/dm^3}$ at RTP. Equal amounts of iron(...
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27 views

How does electrolytic conductance depend on solvation?

My textbook says: If the ions are strongly solvated their effective size will increase and hence their conductance will decrease P.s after reading my textbook, I don't think I'm sure what solvation ...
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Measuring vapour pressure in a closed system

My experiment requires the determination of vapour pressure from which I will calculate the number density (or number of moles of the molecule) later, for a closed system. Here's my setup : Liquid ...
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23 views

What is the value of isothermal compressibility of a van der Waals gas at critical point?

For a van der Waals gas, isothermal compressibility is $$\kappa=\frac{V^2(V-nb)^2}{nRTV^3-2an^2(V-nb)^2}$$ If one substitutes the values of critical temperature and volume in this formula, isothermal ...
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Does the Delta U equals to zero when having Reaction between H2SO4 and NaOH in dilute aqueous solution at constant temperature and pressure [closed]

Reaction between H2SO4 and NaOH in dilute aqueous solution at constant temperature and pressure. Does delta U equals zero in this case? delta H & S as well?!
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IIT JEE Narendra Avasthi Electrochemistry [closed]

QUESTION: Pt (s) | H2(g) (1bar) | (0.1M)NH4OH(aq) || (0.1M) CH3COOH(aq) | H2(g) (1bar) | Pt(s) pKb (NH4OH)=5; pKa (CH3COOH)=5; consider 2.303RT/F=0.06 Volume of 0.1M NH4OH in anode half cell ...
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The glass transition temperature Tg of polymer increases when we have a longer aliphatic side chain group. What exactly happens? [closed]

I understand that thermodynamically, entropy increases when we have a longer side chain. But what about steric hindrance?
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1answer
209 views

Verb for Sorption

Slightly silly question! Intuitively I want the present-simple verb for sorption to be "sorps", but saying it out loud, "sorbs" sounds much more natural. However, Google doesn't turn anything up for ...
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1answer
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Finding initial amount of ammonia using equilibrium constant and amount of nitrogen gas

Question When an amount ammonia is added at $\pu{600 K}$ in a $\pu{1 L}$ container the following reaction takes place: $$\ce{N2(g) + 3 H2(g) <=> 2 NH3(g)}$$ The equilibrium constant ...
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1answer
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How to calculate the molar volume [closed]

In the question at picture, molar volume of liquid water is given as $\pu{0.018 kg mol-1}$. but I don't know how to calculating molar volume of liquid water. Somebody help me plase.
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Kp at a specific temperature [duplicate]

I am unsure how to approach this question, was wondering if anyone could aid me thanks!!! At high temperature, $\ce{2.00 mol}$ of $\ce{BrCl}$ was placed in a $\pu{4.00 L}$ container where it ...
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Explanation for difference in slope of graph of relative lowering of vapour pressure

Can someone tell the reason for the difference in the slope of graph of vapour pressure vs temperature of solid solvent and liquid solvent both the physical (actual process taking place) and ...
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Associated occupation numbers of frozen natural orbitals (FNOs) from MP2 method

The paper Frozen Virtual Natural Orbitals for Coupled-Cluster Linear-Response Theory gives the following (simplified) description of frozen natural orbitals (FNOs). In the MP2 method, the unrelaxed ...
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How to calculate the Kc [closed]

I have attached my question as well: At high temperature, 2.00 mol of BrCl was placed in a 4.00 L container where it decomposed via the following equilibrium, 2BrCl(g) Br2(g) + Cl2(g). At ...
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What is the molar mass of 207mL water [closed]

I can't figure out what one liter of water weighs. From there I could just multiply by 0.207L to have my mass. My confusion lies in if 1 mol is equal to 22.4 Liters, and the mass of water is 18.02 g/...
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Second order reaction with different reactants

In a laser photolysis reaction $\ce{C6H5NH2}$ $(C_0 = \pu{60 µM})$ is oxidized to its radical cation. The disappearance of the cation can follow three pathways: (1) Dimerzing of the cation, (2) ...
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Why does ethanol have a stronger cooling effect on the body than water? [duplicate]

Why does ethanol have a stronger cooling effect than water (i.e. it feels cooler when dropped onto one’s hands) even though water has a higher heat of vaporization compared to ethanol? If we drop a ...
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Why does silver stick to the glass in Tollens' test? [duplicate]

Why does it not simply form a solid powder at the bottom of the flask? Does silver also stick to the glass in other silver precipitating reactions? EDIT: My question is definitely not the same as ...
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How to solve this error in Gaussian09? UNABLE TO DETERMINE LAMDA IN FmD114 [closed]

I'm doing CCSD(T) and CCSD calculations on a series of small molecules. Several calculations terminated without any problems but one CCSD(T) calculation and one utilizing CCSD gave me this error after ...
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Vapour pressure and Boltzmann energy distribution [closed]

As theory says, there is always a certain amount of molecules in a liquid sample which have energies greater than a thresold energy and get free from intermolecular forces in liquid and produces the ...
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How many electrons are exchanged in the following redox reaction? [closed]

$$\ce{\dfrac{2}{3}Al2O3 ->\dfrac{4}{3}Al +O2}$$ I tried splitting the reaction into oxidation and reduction half, but I got stuck. How do you balance the reduction half $\ce{Al2O3 ->O2}$?
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1answer
66 views

Does the property of additivity for the amounts of different substances hold up for ideal gas law?

A mixture contains $\pu{8.00 g}$ each of $\ce{O2},$ $\ce{CO2},$ and $\ce{SO2}$ at STP. Calculate the volume of this mixture. Which of the gases would exert the greatest pressure and why? Here is my ...
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What is the “‡” symbol meaning in a reaction mechanism?

I was studying hydroboration from Clayden's Organic Chemistry [1, p. 1281] and the transition state had “‡” symbol in the upper right corner of the activated complex: We know that this is not the ...
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1answer
102 views

Calculating the biological standard potential

I have an electrochemical cell with following overall reaction: $$\ce{5 Sn^4+ + 2 Mn^2+ + 8 H2O <=> 5 Sn^2+ + 2 MnO4- + 16 H+}$$ I have defined the half reactions as: $$ \begin{align} \ce{Sn^...
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2answers
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Shouldn't the pressure of gas above a liquid slightly decrease when some of its molecules dissolves in the liquid? [closed]

Lets say a liquid and gas above are in equilibrium. (1) Now if I suddenly increase the pressure of the gas it will take some time for some molecules of the gas to enter the liquid and get dissolved. ...
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2answers
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Prove Law of Chemical Equivalence [closed]

A somewhat infamous law (to me at least), that states: $$a.A_{eq}=b.B_{eq}=c.C_{eq}=d.D_{eq}$$ for any and every balanced chemical equation - $$a.A+b.B = c.C+d.D$$ where $i$ denotes the ...
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1answer
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What is the meaning of the J value in term symbols [closed]

I understand how to work out the J values of term symbols. e.g. a d1 configuration gives J values of 5/2 and 3/2. resulting in 2D 3/2 However I dont understand the meaning of it, and why it arises.
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Nitrogen dioxide fluorescence quenching and lifetime

Nitrogen dioxide fluorescence quenching: $$ \begin{align} \ce{NO2 + h\nu &->[$\varphi_\mathrm{Ia}$] NO2^{\ast}}\tag{I}\\ \ce{NO2^{\ast} &->[$k_2$] NO2 + h\nu'}\tag{II}\\ \ce{NO2^{\ast} +...
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1answer
40 views

Water evaporation from calorimeter giving less exothermic enthalpy value?

To find the enthalpy change of combustion for an alcohol, you use a calorimeter filled with water and heat it by burning an alcohol. I was told that usually experimental values for the enthalpy ...
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Why doesn't Delta S total = 0 for this reversible process?

My textbook (Engel Physical Chemistry 3rd Edition) says: For any irreversible process in an isolated system, there is a unique direction of spontaneous change: $\Delta S > 0$ for the ...
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1answer
42 views

Are phase transitions reversible when performed at supercooled temperatures?

For the state transition of supercooled water to ice, is the process reversible? I wonder this because I want to know if I can use entropy change of the universe is 0. If it isn't reversible, how do ...
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What are the limitations of the Born-Lande' equation?

The Born-Lande' equation is used to theoretically calculate the lattice energy, $\Delta U$, of ionic compounds. It is often cited as such in literature, $$\Delta U = -\frac{k_Az_1z_2Me^2}{4 \pi \...
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Why is 50% aqueous hydrochloric acid a generally unavailable reagent?

Why is the highest concentration of hydrochloric acid commercially available generally around the 30-40% range? Has it something to do with evaporation rate, and pressurized storage or standardised ...
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2answers
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How come we can't use the equivalence point equation of NV=NV in this problem?

So, the problem is you prepare to standardize a $\ce{Na2S2O3}$ solution. $\pu{32 mL}$ of $\ce{Na2S2O3}$ solution is titrated into $\pu{50 mL}$ of a $\pu{0.01 M} \ \ce{KIO3}$ solution to reach the ...
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What is the precise meaning of “in-phase” (and “out-of-phase”) in this context?

I am currently studying the textbook Infrared and Raman Spectroscopy, 2nd edition, by Peter Larkin. In a section entitled Symmetry: Infrared and Raman Active Vibrations, the author says the following: ...
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1answer
34 views

thinking about osmotic pressure when liquid is replaced by gas

An option in my test says: "The osmotic pressure of a dilute solution is the same as it would exert if it exists as a gas in the same volume of the solution and at same temperature." I'm not able ...
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1answer
78 views

Product operator analysis for CHn groups in HSQC and HMQC

I'm taking and advanced NMR course this semester and we are learning about product operator formalism. I have a homework where I'm supposed to apply this formalism to an HSQC and HMQC experiment. The ...
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Conversition calculation:unit involving two types of measurement [duplicate]

A certain chemical process consumes water at a rate of 55 Ls−1. Express this water consumption rate in the following units. a. Lh−1 b. kLs−1 c. dLmin−1 d. mLday−1 I did a and b correctly but I ...
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1answer
44 views

Rate law of reactions, what about the proportions? [closed]

Consider the reaction $$\ce{A + B + C -> D + E}$$ and $\mathrm{rate} = k[\ce{A}][\ce{B}]^2.$ My book said if we double the amount of $\ce{A},$ then the reaction rate will double. I understand ...
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1answer
30 views

Raman scattering and “electron and proton center” of molecule

I am currently studying the textbook Infrared and Raman Spectroscopy, 2nd edition, by Peter Larkin. In a section entitled The Raman Scattering Process, the author says the following: Light ...

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