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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Why different Asbestos types are hydrophobic and hydrophilic

I was doing research into the structure of asbestos to see that white asbestos chrysotile is hydrophilic where as both brown and blue asbestos is hydrophobic. Could you please explain why this is?
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58 views

I think elements can be broken down, but their definition says otherwise, why? [closed]

Elements are made up of quarks, right? and physicists have smashed atoms into one another to get quarks, right? Then if the first two statements are true then elements can be broken down into simpler ...
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Rate expression for the final product [closed]

Let's say we have: $$ \begin{align} \ce{A &-> B}&\quad&\text{(fast equilibrium)}\label{rxn:1}\tag{1}\\ \ce{2 B + C &-> D}&\quad&\text{(slow)}\label{rxn:2}\tag{2}\\ \...
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Calculate the energy in the form of heat (in kJ) required to convert 325 grams of liquid water at 20.0 °C to steam at 115 °C

Calculate the energy in the form of heat (in kJ) required to convert 325 g of liquid water at 20.0 °C to steam at 115 °C. Assume that no energy in the form of heat is transferred to the environment. (...
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1answer
404 views

When to use 1/Ka vs Kb [closed]

I'm really unsure what the difference is. We're using these when calculating $K$ of combined reactions. In general, I am also confused what $K$ is in comparison to $K_\mathrm{a}$ and $K_\mathrm{b}$. ...
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2answers
98 views

Find the pH of an amphiprotic salt dissolved in water at room temperature

Let's say I have a polyprotic acid $\ce{H2A}$ with the following properties: $$ \begin{align} \ce{H2A &<=> HA- + H+} & K_1 &= 1\cdot 10^{-1}\\ \ce{HA- &<=> A^2-+ H+} & ...
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41 views

Degree of Hardness Numerical

To remove the temporary hardness from $5\ \mathrm L$ of $\ce{H2O}$ $5.6\ \mathrm{mg}$ of lime is required. Calculate the degree of hardness due to $\ce{Ca(HCO3)2}$ present in water. My attempt: $$ \...
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1answer
131 views

Replacing Salt Bridge with Platinum Sheet

What would happen, if in a galvanic cell, the salt bridge is replaced by an inert platinum sheet? Would charges accumulate on the sheet? Would the cell still work, and produce less emf than earlier, ...
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46 views

Regarding Standard Electrode Potentials

If the standard hydrogen electrode (SHE) is set arbitrarily to have a potential that is equal to 0 V, and has an absolute real potential. Then, in electrochemistry, how are the electrode potentials of ...
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2answers
402 views

When does Hartree-Fock fundamentally fail?

The Hartree-Fock approximation (HFA) works by assuming each electron sees the effective electric field from all the other electrons as some self-consistent field. The HFA is known to give pretty ...
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Free induction decay in NMR (as stated in Pavia)

There is a statement in a very popular textbook of spectroscopy by Pavia (Chapter 3, Intro. to Spectroscopy), it says "The observed FID is actually an interference signal between the radiofrequency ...
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Molarity Numerical on Water Gas Shift Reaction

For the water gas shift reaction below, $K_c = 3.491$ at a certain temperature. What are the equilibrium concentrations of all the components of the reaction if $\pu{0.3815 mol}$ of $\ce{CO}$ and $\ce{...
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1answer
34 views

Meaning of polarization pulse in microwave (rotational) spectroscopy

In the recent rotational spectroscopy literature, "microwave polarization pulse" is often used in conjuction with pulsed Fourier transform microwave spectroscopy (Google Scholar). Sometimes the pulse ...
6
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1answer
54 views

Why is the graph of fluorescence vs. wavelength continuous?

If the emission of a photon from an excited state to the ground state occurs with a precise energy, then why is it that wavelengths that differ from lambda max have values on a fluorescence vs. ...
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2answers
469 views

Can the van der Waals coefficients be negative in the van der Waals equation for real gases?

A gas described by van der Waals equation has the pressure that is lower than the pressure exerted by the same gas behaving ideally. True or false? My approach $$P(\text{ideal}) = P(\text{real}) + P(...
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1answer
70 views

Derive expression for heat flow from oil bath to metal sphere

A spherical ball of iron is put into a hot bath of oil. The iron ball is initially at a low temperature and heat transfer from the oil to the iron will increase the temperature of the iron ball. ...
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24 views

Isobaric-isothermal ensemble with degeneracy

I've been studying statistical mechanics for a while, the topic is very far from what I've learned till now so my questions may be superficial. When trying to see what my entropy is in an isobaric-...
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1answer
45 views

Relationship between rate of reaction and pressure

Given the equation $$\ce{A(g) + B(g) → C(g) + D(g)}$$ with reaction rate given by $$v = k[\ce{A}]^2$$ How can I prove that reaction rate goes up with pressure? I tried substituting $k$ for $Ae^{-...
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1answer
42 views

How will the equilibrium concentration change on adding inert gas at constant pressure? [duplicate]

The given reaction is $$\ce{AB2(s) → A(g) + B2(g)}$$ Now on adding inert gas at constant pressure equilibrium should shift on direction of more gaseous moles. But the answer says that equilibrium ...
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33 views

How to obtain spectroscopic constants Omega_e, Alpha_e, B_e, D_e and D_0 from centrifugal constants?

I need to compute a spectroscopic constants of $N_2^+$ states and I would like to do it using LEVEL16 software, due to its high interpolation flexibility. But it seems, that LEVEL16 can only compute ...
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1answer
68 views

Questions in Equilibrium [closed]

I have two inquiries concerning equilibrium: Does $K_c = 5.0$ indicate that the equilibrium mixture contains both products and reactants at an approximately equal amount? I know that $K_c \approx 1.0$...
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1answer
196 views

Electrolysis of water: Which equations to use? (IB Chem)

There is a list of standard electrode potentials at 298 K from the p. 23 of IB Data Booklet 2016. Which of the following equations (forward/backward reactions), from the two possible ones involving ...
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1answer
68 views

Proving a relation for fugacity of component i in term of independent variables (T,V)

In Molecular Thermodynamics of fluid phase equilibria by Prausnitz et al. [1] the authors recommend to use the following equation which gives the fugacity of component $i$ in terms of independent ...
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Why do old black and white photos fade?

I understand why photos based on organic dyes would fade (discussed previously). But photos based on metallic silver fade as well such as like the one shown below. As a metal (a fairly stable one at ...
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1answer
62 views

Maximum number of atoms in the ground state

I was given the following question. A sample contains $100$ identical and hypothetical $H$-like atoms ( $Z$ may be fractional). Out of the given atoms, some are in the ground state, while others ...
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2answers
95 views

Scientific Reason for Salt Solution Gaining Volume

A little background to this question: my mom placed a glass with salt and enough water to just cover the salt in a room to "absorb negative energy" out of the room at her office. It obviously "worked"....
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1answer
94 views

Gibbs Free Energy and Maximum Work

I am a high school student and my professor mentioned that the Gibbs free energy is the maximum amount of work (or useful work) that a system can do, whereas entropy is a measure of the non-available ...
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20 views

Hydrogen peroxide and carbon as hybrid rocket propellant?

I was thinking that a hybrid rocket could be made using hydrogen peroxide and activated charcoal or some other carbon source. Step 1: Decompose hydrogen peroxide to steam and oxygen, as in a ...
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2answers
89 views

Why is reduction potential of water ( 2H₂O + 2e⁻ → H₂ + 2OH⁻ ) is -0.83 insted of 0, as in the case of (2H⁺ → H₂)?

I came across this value of reduction potential of water while solving a question. Also, I noticed that, for example $$\ce{Ag+ → Ag}$$ has a fixed standard potential, and the same is used when we do ...
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3answers
3k views

Is it possible to boil a liquid by just mixing many immiscible liquids together?

In open air, when vapour pressure reaches 1 atm, boiling takes place. I read that if we add two immiscible liquids together, the total vapour pressure of the 'mixture' is close to $p = p^*_A + p^*_b$,...
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Calculating Air Density and Effect of Air Composition

I have to calculate density of atmosphere, assuming that it is: 79% : N2 21% : O2 Does the percentage of gases affect the answer, and how can we find the density with such little information?
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1answer
71 views

Enthalpy change of gas expansion against constant external pressure

A certain mass of gas is expanded from $\pu{1 L}$ at $\pu{10 atm}$ to $\pu{4L}$ at $\pu{5 atm}$ against a constant external pressure of $\pu{1 atm}$. If initial temperature of gas is $\pu{300 K}$ and ...
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63 views

How to derive the compressibility factor for a van der Waals gas?

So as far as I know, $$Z=\frac{p_\mathrm{r}V_\mathrm{r}}{nRT},$$ where $\mathrm{r}$ denotes the subscript for real. Solving it for a van der Waals gas gave me the following result, $$Z=1+\frac{p_\...
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2answers
93 views

Oxidation of metals/halogens by oxygen gas in acidic aqueous solution

I had some confusion about the correct answer to the following question: Which substance can be oxidized by $\ce{O2(g)}$ in acidic aqueous solution? Two of the answer choices were metal cations (...
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2answers
56 views

Which substances have the highest/lowest enthalpy of formation per gram?

Which substances have the most extreme enthalpies of formation per gram at standard temperature and pressure?
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2answers
134 views

Compressibility Factor Of Gases

In the general equation of the compressibility factor $Z$, we define $Z$ as $$Z=\frac{pV}{nRT}$$ Here, what is $p$? Is it $p_\text{real}$ or $p_\text{ideal}$? Also, what is $V$? $V_\text{real}$ or $V_\...
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1answer
51 views

Gravimetric analysis

In a gravimetric determination of phosphorus an aqueous solution of dihydrogen phosphate ion is treated with the mixture of ammonium and magnesium ions to precipitate magnesium Ammonium Phosphate. ...
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1answer
167 views

Only d orbital electrons for spin only magnetic moment

During my chemistry lessons and self studies, I have come upon many instances where I observed that during calculations of spin only magnetic moment of transition elements only the d orbital electrons ...
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2answers
70 views

Is Gibbs energy change during osmosis positive? If so then why is it spontaneous?

For ideal solution, μA=μA* +RT lnxA ln function is an increasing function, means that the higher the xA the higher the μA......(1) Now consider osmosis. From Atkins' Physical Chemistry Ninth ...
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28 views

Calculate chemical potentials to find electrode Fermi level

I'm running some simple simulations of the semiconductor-electrolyte interface and I'm having a hard time figuring out the equilibrium condition. Can someone please help me with my electrochemical ...
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1answer
32 views

Finding simplest formula of a compound with following specifications

I ran into the following problem, wherein I'm asked to find the simplest formula of a compound containing $50 \%$ of element $X$ (atomic wt. 10) and $50\%$ of element $Y$ (atomic wt. 20). I know ...
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1answer
34 views

What are we seeing in this AC salt-water copper-wire experiment?

There's a highly watched video on YouTube by "ElectroBoom" on the effects of passing AC (not DC) current through salt water. The water gets cloudy and at the end of the video we can see one of the ...
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24 views

Relation between size and lattice energy

I came across the statement “BeO and MgO have high melting point because of the lattice energy of BeO and MgO is appreciably high due to their small size” in my mAterial I didn’t understand what ...
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1answer
32 views

Is temperature of crystallisation same as melting point temperature for polymers?

Melting point tends to be a temperature range. Is it true that the temperature of crystallisation is the highest temperature at which the polymer melts and thus there is some distinction between ...
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1answer
58 views

Heat of formation of aqueous H⁺

In my book it is given that by convention heat of formation of aqueous $\ce{H+}$ is taken to be zero. Heat of formation is energy released or absorbed when 1 mole of a compound is formed from its ...
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Derivation of equilibrium constant [duplicate]

In general chemistry, we learn that the equilibrium constant, defined in terms of activities, for the reaction $$\ce{aA + bB -> cD + dD}$$ is given by $$K_\mathrm{eq} = \frac{(\ce{C})^c(\ce{D})^...
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For azeotropic mixtures, is the total vapour pressure at equilibrium equal to the partial pressure of one of the components?

I know, a ridiculous statement. But here's how I reached at it . Say we have a solution of two components liquids A and B. By Raoults law, $$p_A= p_A^o \times x_A \tag1$$ Also by Dalton's law, $$...
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3answers
52 views

Changing the order of the reaction with change in concentration

The reaction $$\ce{2 A + B + C -> D + 2 E}$$ is found to follow the rate law as $$r = k[\ce{A}][\ce{B}]^2[\ce{C}]^0$$ If the concentration of $\ce{A}$, $\ce{B}$ and $\ce{C}$ increases two times ...
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0answers
23 views

Perturbation theory for molecules, chromophore group, dipole approximation,

I am interesting in chromophore group and dipole approximation. For example, i have a molecule (acetone or any other ketone/enol) which is belongs to some symmetry group. Because of the symmetry ...
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2answers
66 views

What happens to the pressure of gas when only one molecule of it is placed in a very large container?

We say that pressure due to gas is constant throughout the container. Pressure is created by molecules present in it. When there are many molecules I agree that they can apply the same pressure all ...