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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Relative Humidity, vapor pressure, partial pressure

The partial pressure of water in the mixture is the equilibrium vapour pressure of water at the temperature specified. Relative humidity (RH) is the ratio of the partial pressure of water vapor to ...
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What substance would crawl out of a vessel?

I remember in my first chemistry lessons at high school my teacher told us about atomic properties of materials elastics and stiffness and what ever else. At one point he came up with an example of an ...
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Alkali metals and viscosity

I've recently conducted a viscosity experiment to find the relationship between alkali metal ions, the concetration of the solution, and the viscosity of the solution. We used the Oswald viscometer to ...
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How to determine concentration limits of a buffer that's limited by solubility?

I need to maintain a certain range of % of ionisation from a buffer. For e.g. Histidine buffer. When making high concentration of this buffer at (say) pH 7.2, 25'C, [concentration] is limited to 75mM ...
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Extimating the repartition of water between hygroscopic compounds

Sulfuric acid is sometimes used as a drying agent. According to literature, one possible application is, for instance, in the drying of bromine. Some questions came to my mind: which concentration ...
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Comparison of ways to provide energy to a reaction

As we all know, you can provide energy to a reaction to overcome the activation energy of a reaction by heating the reaction. I have, however, recently sat through a talk where someone 'powered' a ...
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Physical Chemistry: Calculating ΔG, ΔH, ΔS on a given equation

This question was brought in class, but I have no clue if my answer is correct or not. I wonder if you guys can double check my answer. Between $\pu{0 ^\circ C}$ and $90 ^\circ C$, the potential ...
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2k views

Finding the rate constant of a first order reaction

The reaction $\ce{A + B -> AB}$ is 1st order with respect to A and zero order with respect to B. The reaction is begun with the initial concentration of both reactants at $0.100 \,\text{...
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476 views

What is the need for dipole moment if electronegativity already exists?

Say we have an HCl molecule. The difference in electronegativities of the H and Cl atoms tells us how polar the HCl molecule is. The dipole moment is also a measure of the degree of polarity in ...
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pH calculation in case of amphiprotic ion

$100\ \pu{ml}$ of $0.1\ \pu{M}\ \ce{H3PO4}$ is titrated with $0.5\ \pu{M}\ \ce{NaOH}$ solution till 2nd equivalence point. Then resultant solution was mixed with $10\ \pu{ml}$ of $0.5\ \pu{M}\ \ce{HCl}...
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rate constant via flux-flux correlation function for linear potential energy surface

How does one calculate fully quantum mechanical rate ($\kappa$) in the golden-rule approximation for two linear potential energy surfaces? Attempt: Miller (83) proposes $\kappa=\int{Tr[\exp{(-\beta\...
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Chemical theory, formula(s) that predict final *volume* of a solution?

I asked this question a couple years back regarding the volume of a mixture being less than the volume of the original solute and solvent, but this question asks if there is theory and/or formulation ...
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66 views

Does the frequency of incident light change in Beer-Lambert Law?

The Beer-Lambert law is meant to describe the interaction between a solute and incident light. But, does the frequency of the light here change due to the interaction with molecules? I think there ...
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383 views

Aluminum powder reaction with air

I have made aluminum powder in a ball mill a few times, but my last batch began to smoke and caught fire soon after I poured it from the tumbler. Nothing unusual was afoot. It was poured into a paper ...
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196 views

How to determine the permissible values for which solution of the Schrödinger's wave equation exists?

My textbook( A Textbook of Physical Chemistry, Dr. O.P. Tandon ) says that solution of the Schrödinger's wave equation exists only for certain permissible values which are called eigen values.( ...
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Are molecules on surface of liquid stationary due to surface tension

Are the molecules which are on the surface of a liquid ie the molecules on the top film stationary ie not move about each other under steady conditions ie unlike molecules in the bulk because of ...
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234 views

determination of glucose syrup in sugar product

I work with a sugar product that contains saccharose (approx. 70 %), glucose syrup (approx. 15 %), glycerine (approx. 3 %) and some other ingedrients, e.g. water. Glucose syrup consists of 5 % glucose ...
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365 views

NAMD free energy calculations (FEP, Alchemical)

I am trying to calculate the absolute free energy of a protein-ligand-complex using the free energy perturbation theory. Following the alchemical route in this tutorial, I have calculated eight MD-...
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686 views

Problems with Daniell cell

In Zemansky and Dittman's book on thermodynamics, pages 41–43, the authors discuss the Daniell cell as a thermodynamic system. Their cell consists of two saturated $\ce{CuSO4}$ and $\ce{ZnSO4}$ ...
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647 views

Why is the degree of dissociation for a weak acid α, but for a weak base, it's 1−α?

From the equation used in this answer: Calculating charge on amino acid from pKa $$\alpha=\frac{1}{10^{\mathrm pK_\mathrm a-\mathrm{pH}}+1}$$ Degree of dissociation of weak acid is $\alpha$. However,...
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How to tell if a vibrational mode in benzene is IR and/or Raman active?

Consider the vibrational mode that corresponds to the boat-like bending of a benzene ring. Is it (i) Infrared active? (ii) Raman active? This question was asked in an assignment in my college. ...
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Why does changing the dilution of an aqueous equilibrium shift the equilibrium?

Say we have the equilibrium $$\ce{A_{(aq)} + 2B_{(aq)} <=> C_{(aq)} + D_{(aq)}}$$ meaning the formula for the equilibrium constant is $$\ce{K_{c} = \frac{[C][D]}{[A][B]^2}}$$ My understanding is ...
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Equilibrium Problem Involving Solids: Faulty?

I am convinced that this is a faulty problem: $\ce{2 Cu + S -> Cu2S}$ For the reaction above, $\Delta H$, $\Delta S$, and $\Delta G$ are all negative. Which of the substances would ...
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3k views

Which of the following pairs show common ion effect?

Which of the following pairs show common ion effect? $\ce{BaCl2}$,$\ce{Ba(NO3)2}$ $\ce{NaCl}$, $\ce{HCl}$ $\ce{NH4OH}$,$\ce{NH4Cl}$ $\ce{NaOH}$, $\ce{NaCl}$ Its not (1) because they ...
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827 views

Balancing molecular and net ionic equations for reactions

Source:'Chemistry: The Central Science 11th edition' by Brown. Ch.4, 4.53: Question: Write balanced molecular and net ionic equations for the reactions of: chromium with hydrobromic acid; ...
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Concentration of NaIO3 using hypo

$$\ce{2NaIO3 + 5NaHSO3 -> 3NaHSO4 + H2O + I2 + Na2SO4}$$ $\mathrm{20ml}$ of $\ce{NaIO3}$ solution reacted with excess $\ce{NaHSO3}$ releasing $\ce{I2}$ that can oxidize $\mathrm{20ml}$ of $\...
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537 views

Preparation of ferric hydroxide sol

I have read that before the preparation of ferric hydroxide sol, the beaker must be cleaned by the steaming out process, while it is not necessary for starch sol. Why is that?
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27 views

Solvation rates of crystalline and noncrystalline materials

Assuming equal surface area (and other variables), would a highly ordered crystal of some substance dissolve more slowly or quickly than (or at the same rate as) a disordered sample of the same ...
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Why isn't Graham's Law working here?

In graham's law of diffusion most numericals I have seen assumes the formula $$\frac{r_1}{r_2}=\frac{P_1}{P_2}\sqrt{ \frac {M_2}{M_1}}$$ Where they say $P_1,P_2$ are the partial pressures of the ...
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247 views

Active mass,Pressure and concentration

The concentration is connected to the activity via $$a(\ce{A})= \gamma_{c,\ce{A}}\cdot{}\frac{c(\ce{A})}{c^\circ},$$ where the standard concentration is $c^\circ = 1\:\mathrm{mol/L}$. At reasonable ...
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678 views

What are some factors that influence the voltage of voltaic/galvanic cells and why?

Question: (2014 USNCO local exam Q#41): What types of changes would increase the voltage of a voltaic cell. I have learned a bit about voltaic cells, but I haven't been able to find information ...
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478 views

Calculating the wavelength of an emitted photon of a Ne^9+ ion

I'm supposed to calculate the wavelength of an emitted photon going from the 6p orbital to the 2s orbital. The first part of this problem will be to use the equation $$E=-{Rh\over n^2}$$ in order ...
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114 views

Quantum Numbers

Why are the Lanthaide (atomic #'s 57-71) elements in period 6, but in terms of electron configuration, are assigned the principal quantum number of 4? Why are certain subshells assigned quantum ...
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260 views

Difference between starch surfactant and CTAB, SDS, Tx-100

I am doing a research on the effect of surfactant on ZnO nanoparticles properties. There is a confusion here between starch surfactant and CTAB, Tx-100 and SDS. I need point on what is the difference ...
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82 views

How to minimize surface adsorption by choice of material?

I need to do buoyancy experiments in vapours consisting of organic molecules in air using a microbalance. This involves measuring the change in weight of a sealed glass sphere when exposed to the gas. ...
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113 views

Have Mossbauer spectroscopy on 67Zn ever been used to study Zinc containing enzymes?

Have Mossbauer spectroscopy with 67Zn as absorber and 67Ga as emitter ever been used to study zinc containing enzymes? The perfect answer will contain link to article/book where example of 67Zn usage ...
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123 views

Titration of alpha-amino acid with strong base

Question: $\mathrm{50~ml}$ of the conjugate acid $\ce{H3N+CH(R)COOH}$ of an $\alpha$-amino acid required $\mathrm{30~ml}$ of $\mathrm{0.1~M}~\ce{NaOH}$ to completely convert into the dipolar ion $\ce{...
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O-N-O bond angles in oxides of nitrogen

If we look at the bond angles of O-N-O in figure (c), (D) and (F), there not too much change in bond angle. Even though they are notable. So my question is, Why do we observe very small change in ...
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Is there a specific chemical property or concept that explains/predicts the triboelectric series?

Is there a chemical property (perhaps electron affinity?) that can be used to predict where a substance would fall in a triboelectric series such as this one? Or would the cause of the charge ...
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73 views

Oil refinery - How many plates are needed for a 10 degrees difference in temperature?

I am having some trouble going about this question. My first thought is to set up an ASTM separation equation to figure out the difference, but I do not know how to incorporate the reflux ratio which ...
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33 views

Computing initial reaction speed given reaction constant

Problem: $\ce{N2O}$ falls apart in oxygen gas and nitrogen gas according to a first order reaction rate. If you know that the rate constant is $0.38\ \mathrm{s^{-1}}$ at $760\ \mathrm{^\circ C}$, ...
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249 views

Interaction between soy milk and coffee producing bubbles

I noticed when I poured my soy milk (which I shook as per the directions on the carton) into my coffee, a large number of very fine bubbles rose to the surface. What causes this? Is there a chemical ...
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Relationship between Equivalence Ratio and Adiabatic Flame Temperature for Fuel Rich Combustion

I'm reading a combustion text and would like help interpreting the following passage (diagram attached). It is regarding the relationship between equivalence ratio and adiabatic flame temperature: ...
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336 views

Are forming coins starting with sodium chloride possible without the clay melting from the molten metal?

Is forming metal coins (specifically ones with copper, nickel, and zinc) possible with these steps: Carve a sheet of sodium chloride so that it is big but not too big and so that the design sticks ...
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864 views

Structure of fluoroalkylsilane

I want to use FAS (fluoroalkylsilane) in my molecular dynamics study. How can I find it's real structure? So that I can find proper forcefield for simulating the molecule. It would be very nice if you ...
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414 views

How do I measure the density of a cellulose acetate membrane?

I've been playing around with filtration methods, and got my hands on a casting machine for this purpose. My first mission was to find out how porosity can affect filtration. To see this for myself, ...
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245 views

Graph theory, isomer enumeration and chemical graph theory

Where could we find a good description of graph theory applied to the general problem of isomer enumeration and chemical graph theory?
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102 views

Making a reasonable slab of alpha quartz

I want to perform a molecular dynamics simulation with alpha-quartz as my mineral surface. I want to study adsorption of water on alpha-quartz. The most dominant error that I came up with is the ...
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124 views

Why does confinement of quantum dots result in discrete energy levels?

I'm doing a project with lead (II) sulfide quantum dots because they have optical transitions in the near infrared. I understand the simple "particle in a box" approach where confinement strengthens ...
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Magnetic moment of coordination complexes?

To understand the commonly quoted magnetic values of coordination complexes (central ion) we use $$m_l=\sqrt{n(n+2)} \text{BM where BM}=\frac{e\hbar}{2m_e}\text{JT}^{-1}$$ $n$=number of unpaired ...

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