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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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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268 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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2k views

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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343 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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898 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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426 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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103 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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133 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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88 views

Reference to find dielectric constants and dielectric relaxation time

I am working on a Master degree and need to know the following data : The static (low frequency) dielectric constant of isopropanol at 25 °C The Optical (high frequency) dielectric constant of ...
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1answer
123 views

Is every substance in equilibrium with its vapours?

In one of my previous questions, I got an answer from user Jan: The smell of a compound as we perceive it usually depends on which receptors in the nose will bind the molecule (or not). These ...
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1answer
589 views

pKa of Tris corrected for ionic strength

I have a question regarding the molar fraction calculation of Tris buffer at different temperatures. Tris dissociates according to the following equation: $$\ce{Tris + H2O -> Tris+ + OH-}$$ So, ...
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3answers
130 views

How does the equilibrium shift when concentration of reactant and product are increased simulatenously

Before answering my question, take a look at this example $$\ce{2NOCl <=> 2NO + Cl2}$$ Let's suppose I have 2 mol/l $\ce{NOCl}$, 2 mol/l $\ce{NO}$, and 1 mol/l $\ce{Cl2}$ in a closed system. ...
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36 views

Approximating entropy change in a reaction using Arrhenius equation

I am a high school student.Recently my teacher finished teaching the chapter Chemical kinetics in which I have gone through Arrhenius equation.Can we estimate the change in entropy using it? I have ...
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54 views

Applying Bohr's model for Helium atom

Consider the following atomic model for Helium. Helium contains 2 electrons revolving in circular orbit around the nucleus,in such a way that there is minimum possible repulsion between them.Calculate ...
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26 views

Software for modelling decomposition reactions

What are some good softwares that can model a decomposition reactions? I have a reaction of H2O2 decomposing on metal exchange hexaaluminate catalyst. The catalyst is present in a packed bed thruster. ...
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1answer
44 views

Electrolysis using electrodes of metals whose ions are in solution

So when we perform electrolysis of say an aqueous solution of silver nitrate with silver electrodes, silver ions having a greater reduction potential than water, accepts electrons and deposits at the ...
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1answer
46 views

At what composition is Maximum deviation from Raoult's law observed?

Raoult's law states that in an ideal binary solution of two volatile components, the partial vapour pressure of each component is proportional to its mole fraction in the solution. A plot of total ...
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27 views

Primary kinetic isotope effect

Why does the transition state in both protonated and deuterated molecules have the same energy? My textbook assumes that during transitional state the isotopic bond is half-broken or on its way to ...
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29 views

When, if ever, can standard enthalphy be subsituted for standard chemical potiential?

I'm reading through a combustion modeling paper by Gordon & McBride which is a bit scant on some of the algebra & calculus used to derive their equations. My advisor and I have derived nearly ...
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32 views

Gibbs function for pure substances

I know that the Gibbs function for pure substances is given by $$\mathrm dG = V\,\mathrm dp - S\,\mathrm dT.\tag{1}$$ However, I also saw the same equation in the form $$ΔG = VΔp - SΔT,\tag{2}$$ ...
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24 views

Constructing a partition function for a gas-solid equilibrium in canonical ensemeble

For a closed system at fixed N,V,T there is a solid in equilibrium with its vapor. I'm told that I can minimize the helmholtz free energy to find that the equilibrium condition is given by $N_g = \...
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46 views

Wave function of a harmonic oscillator

In a question it is given that consider $H-X$ chemical bond and find $H-X$ bond distance for which there is zero probability density of finding the proton. It is easy to solve we have just to ...
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26 views

Constructing phase diagram given temperature-concentration-phase data

This question may look straightforward to be answered but somehow I can not figure it. I received these papers [1-2]. Here, the papers (both papers study same system) provide complete information of ...
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16 views

Pressure of a system of particles

I'll derive the pressure of a system of particles, which would be used in a MD simulation for example, according to Allen's Computer Simulation of Liquids and show where my issue is. Consider a ...
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30 views

Calculating Ka using Nernst Equation

I've heard multiple times that the Nernst Equation could be used to calculate K$_a$. How would one calculate the acidity constant, K$_a$, of a specific acid, using the Nernst Equation? The equilibrium ...
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39 views

How to find relative lowering of vapour pressure from phase diagrams in terms of temperature?

Problem Answer My question Does a tie rule exist for solution solvent phase diagram to express relative lowering of vapour pressure in terms of temperature? The phase diagram is the one ...
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26 views

Specific conductance of KCl

Question: A conductivity cell containing distilled water has a resistance of $\pu{454 k \Omega},$ while the same cell containing $\ce{KCl}$ solution prepared in the same sample of water shows ...
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34 views

Effect of optical isomerism on colour of transition metal complexes

I know that different stereoisomers of a given transition metal complex (cis- and trans- forms) have different colours. But do different optical isomers (non-superimposable mirror images) have ...
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9 views

Comparison of acidity of aqueous solutions of Lewis Acids

What can be the order of acidity of aqueous solutions of following Lewis acids: $\ce{FeCl3, AlCl3, BeCl2, NiCl2}$ The simplified reactions are: $\ce{FeCl3}$: $\ce{FeCl3 + 6H2O -> [Fe(H2O)6]^3+(...
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49 views

Effect of ionization on dipole moment

Suppose we have a non-dipolar molecule such as carbon dioxide. If carbon dioxide is ionized by some means in the gas-phase, will it develop a dipole moment? I am asking with reference to microwave ...
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34 views

What is the activation energy of a Daniell cell?

I'm having trouble finding a posted literature value for the activation energy for the Daniell cell redox reaction: $$\ce{Cu^2+ + Zn -> Cu + Zn^2+}$$ Where might I be able to find this ...
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70 views

Determining molar mass of protein from osmotic pressure

A 299 mL solution containing 21 g of a protein in toluene had an osmotic pressure of 0.053 atm at 27 degrees Celsius. What is the molar mass (in g/mol) of the protein? We can use the formula that $$\...
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18 views

Maximum Value of Monolayer Capacity

What is the possible maximum value of the monolayer capacity? Is it possible for the monolayer capacity to exceed more than $(100)\frac{mol}{g}$ or even $(1000)\frac{mol}{g}$? Any help is highly ...
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1answer
836 views

Why Freundlich adsorption isotherms fails at high pressure conditions?

Experimentally it was determined that extent of gas adsorption varies directly with pressure, and then it directly varies with pressure raised to the power 1/n until saturation pressure Ps is reached. ...
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42 views

Effect of drinking on internal energy and entropy of the universe

I have just been doing some questions on thermodynamics and have come across a strange question that I can't seem to grasp. The question asks me to estimate the change in body temperature as well as ...
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18 views

LIF spectrum with laser-coupled levels lines as the strongest

Why, if I excited the OH molecule Q-branch transition, my LIF spectrum (recorded during and after the laser pulse) does not result in only Q line being the most prominent, but also P and R lines with $...
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1answer
115 views

Enthalpy of reaction between ammonia and oxygen

I have to ask this here because I asked literally everybody I know and I still disagree with them. Using the information in the table below, calculate the heat of released from the following ...
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26 views

To calculate expansion work for a process

[1 mark] To calculate the expansion work for a process, 1) the formula $w = -P_\mathrm{ex}(V_2 - V_1)$ always works under all conditions. 2) the formula $\mathrm dw = -P_\mathrm{ex}\,\mathrm dV$ ...
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36 views

In UV photoelectron spectroscopy why are filled orbitals seen at a higher binding energy?

I understand that the partially filled Ni intersects the Fermi level as there is a change from filled to unfilled orbitals. But what is the explanation for the lower binding energy of the filled 3d Cu ...
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46 views

Difference between liquid and solid stearic acid

I had some stearic acid in solid pellet format. It is slippy and in white color. I used this to make some experiments. I recently notice that some manufacturer can supply liquid stearic acid. I ...
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25 views

What could be causing a small uptick in FCS curve at approximately 10 microseconds

I work as an RA in an academic lab. I've been working with FCS fitting for an experiment, and took FCS curves for fluorescein and calmodulin, displayed with residuals below: ]2 I fitted both to an ...
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57 views

Methylhydrazine Calorimetry

Below is a chemistry practice problem. I am curious why the change in heat of the oxygen molecules doesn't affect the calculations. Methylhydrazine ($\ce{CH6N2}$) is commonly used as a liquid ...
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16 views

Inductively Coupled Plasma and Mass Spectrometry

I was doing some homework and I was reading about how ICP is suitable for mass spectrometry and it said how its high temperature favours ionization which is good in MS. But also, because the ...
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34 views

Can we break double bonds by using laser and heat?

If it is possible then give an example for it. That chemical reaction is in this process. step 1: {Reactant + heat(sunlight)} gives weakened bonded product1 step 2: {product1 + laser} gives {one solid ...
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1answer
51 views

Why does eutectic point has three phases, but consolute point has two phases?

At eutectic point, there are three phases: solid A, solid B and homogenous liquid phase containing both A and B. But at consolute point, we are told it has 2 phases: liquid A and liquid B. Why isn'...

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