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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How to calculate the required concentration for sodium sulfite to remove oxygen as an oxygen scavenger from a solution?

If I know the amount of oxygen in such a solution, how can I know the required concentration of sodium sulfite to be used and react as oxygen scavenger?
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19 views

Is ln(K2/K1) = (∆h°rxn/R)(1/T1 - 1/T2) even when ∆h°rxn varies strongly with temperature?

In all of my physical chemistry books I find the same expression for estimating the equilibrium constant of a reaction at a non-standard temperature. The derivation starts with $R \ln K_\text{eq} = ...
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1answer
133 views

What is a catemer?

What is a catemer and how does it differ from a dimer? What type of compounds could form catemers and how does their formation influence its crystal structure?
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45 views

What is the CO2 content in the air in a compartment of air and water, as a function of temperature?

What is the graph of carbon dioxide ($\ce{CO2}$) content in the air in a compartment consisting of 80 percent air and 20 percent ocean sea water as a function of temperature, in the temperature range ...
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24 views

a chemical model for pde

Consider the initial boundary value problem $$u_t=a(t)u_{xx},\,\,\,0<x<1,\,\,\,t>0$$ $$-ku_x(0,t)=hu(0,t),\,\,\,t>0$$ $$u(1,t)=u_0,\,\,\,t>0$$ $$u(x,0)=f(x),\,\,\,t>0$$ where ...
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15 views

Why are the axial bonds of PF5 longer than those of the equatorial bonds? (Hybridization)

The axial bonds of $\ce{PF5}$ are longer than those of the equatorial positions. One explanation is that because the axial bonds are experiencing more repulsion than those of the equatorial and ...
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1answer
43 views

Why is the conductivity of non-metals not equal to zero?

My chemistry book says that delocalized electrons are the reason for electrical conductivity in a metal. However it says that nonmetals like sulfur, phosphorus and silicon have "low" conductivity. How ...
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25 views

Why are multiple oxidation states useful for a catalyst?

Transition elements are good catalysts because they have multiple oxidation states?Why multiple oxidation states matter?
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32 views

Is it possible to dope Ca ions in an NaCl crystal to produce a vacancy defect?

I was just reading about defects and doping in solids and read about the defect in ionic crystal ($\ce{NaCl}$). There were examples of $\ce{SrCl2}$. Could this also occur with $\ce{CaCl2}$?
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18 views

Raoults law: Is the molar fraction the molar fraction in the entire system?

Atkins book talks about the molar fraction term in Raoults law as if it were of the entire system. Levine says that Raoults law has the form $P_i = x^l_i P_iº$ which looks as if she were saying that ...
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1answer
28 views

How to calculate the temperature at which a reaction becomes spontaneous?

At $25~^\circ\mathrm{C}$, $298~\mathrm{K}$,, the reduction of copper(I) oxide, $ \Delta H = 58.1~\mathrm{kJ}$, $\Delta S= 165~\mathrm{J/K}$, is nonspontaneous, $ \Delta G = 8.9~\mathrm{kJ}$. ...
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20 views

Why does ionization energy increase as we go from left to right in a period?

Why does ionization energy increase as we go from left to right in a period? In my textbook, the explanation is as follows: "This is consistent with the idea that electrons added in the same ...
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1answer
18 views

Distance between successive tetrahedral voids in FCC

What is the distance between successive tetrahedral voids in a FCC Crystal structure? The distance between a face centered atom and a tetrahedral void is $\sqrt{\frac{3a}{4}}$ if the cube's edge ...
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1answer
46 views

Why is i-butane more stable than n-butane?

I would like to understand the term stability in organic chemistry. We know empirically that i-butane is more stable than n-butane. But why is it more stable? Is it because of formation enthalpies or ...
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40 views

Why is it that increasing the molar mass generally increases the Entropy?

I've just found read that entropy increases through these reasons: Changing the phase of the elements to a gas. Increasing the molar mass of that specific element increases the entropy. I ...
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1answer
21 views

Hess's Law - enthalpy of combustion

The enthalpy of combustion of a solid carbon to form carbon dioxide is $-393.7\ \mathrm{kJ/mol}$ carbon, and the enthalpy of combustion of carbon monoxide to form carbon dioxide is $-283.3\ ...
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1answer
152 views

Exo- or endothermic? Clarification required regarding a few cases

Are the following processes exothermic or endothermic? a) When solid $KBr$ is dissolved in water, the solution gets colder. b) Natural gas ($CH_4$) is burned in a surface. c) When concentrated ...
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1answer
79 views

Do I have to consider the molecular mass of the oxygen atom or the diatomic oxygen molecule when determining the empirical formula of an iron oxide?

In determining the empirical formula of a compound which constitutes a diatomic molecule, should we calculate the molar mass of the divalent molecule by multiplying the molar mass of the element by 2, ...
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1answer
107 views

Gas Stoichiometry - where is my mistake in dealing with this problem?

A $20.0$-L nickel container was charged with $0.500$ atm of xenon gas and $1.50$ atm of fluorine gas at $400$ $^{\circ}$C. The xenon and fluorine react to form xenon tetrafluoride. What mass of xenon ...
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1answer
29 views

Using enthalpies of formation and combustion to find formation enthalpy of Acetylene (Hess' Law)

I understand this is a simple question (I’m in high school), but for some reason the numbers just are not working for me. Given: $$\Delta H^\circ_\text{c} = -1301\ \mathrm{kJ}\ \text{for}\ ...
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2answers
44 views

Relation between molar mass and van der waals force

In the book that I'm reading it is mentioned higher molar mass results in stronger van der waals force, but didn't continued why. I wonder why is that so? molar mass is actually dependable on the ...
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14 views

Spectral reflectance identification of types of iron rust

According to the Wikipedia page about rust, there are red and green types of rust that occur on iron. Red rust is the reaction with oxygen and water and the green with chlorine (in oxygen poor ...
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1answer
25 views

Color of Phenomelanin?

Do we know what is the wavelength of the color of Phenomelanin? If not, can we use the color of Phenomelanin-rich areas, like the lips, to discern the color of Phenomelanin?
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2answers
29 views

How do I create azeotrope mixture?

I want to decrease the boiling point of a compound. So I need to create an azeotrope mixture from two or three compounds. Where can I find out how make it?
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1answer
29 views

Ratio between heat tranfer coefficient and thermal conductivity

Consider the Robin boundary condition for the diffusion/heat equation $\mathrm{u_t=a(t)u_{xx}+f(x,t)}$: $$\mathrm{-k(t)u_x(0,t)=h(t)u(0,t)}$$ or $$\mathrm{u_x(0,t)+\frac{h(t)}{k(t)}u(0,t)=0}$$ ...
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Why does water evaporate spontaneously at room temperature despite dG > 0?

Standard Gibbs free energy of formation of liquid water at 298 K is −237.17 kJ/mol and that of water vapour is −228.57 kJ/mol. Therefore, $$\ce{H2O(l)->H2O(g)}~~\Delta G=8.43~\mathrm{kJ/mol}$$ ...
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1answer
59 views

What is the difference between the units 'torr' and 'mm of Hg'?

According to present definition torr and mm of Hg differ though slightly. I am still confused over it. Can someone write an explicit answer differentiating between them and the reason for ...
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2answers
185 views

How to find the second order perturbation to wave function?

Today, I'm looking for how to find the 2nd perturbation to the base in Rayleigh Schrödinger Perturbation Theory (RSPT). SETUP Starting from the 2nd order perturbation in Dirac's notation: ...
3
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1answer
42 views

Lennard-Jones potential and vibrational energy level diagram explanation

I don't understand how to interpret graphs like the following: Forget the difference between the Harmonic and Morse (I think I get that), It's more what the horizontal lines mean and what the ...
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0answers
22 views

How was it determined that the electron observed in the cathode ray experiments was the same particle that gave an atom its balancing negative charge?

How was it determined that the electron observed in the cathode ray experiments was the same particle that gave an atom its balancing negative charge? Couldn't there have been an entirely different ...
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41 views

How to determine limiting conductivity of specific ions?

Given a table with equivalent conductivity of certain electrolytes, how can I determine the conductivity of separate ions? I know that you can find the difference between for example K+ and Na+ if you ...
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25 views

How do tie-line slopes affect raffinate/extract envelope in ternary phase diagrams?

I am struggling to understand ternary phase diagrams for reactor engineering. The course slides offer little to no help so I'm hoping to find an answer to this question How does the slope of the ...
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1answer
41 views

Is an acid a liquid or an aqueous solution? [closed]

I am tying to determine if an acid is a liquid or aqueous solution? Please can some one enlighten me?
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26 views

Which species can't appear in the rate expression for this reaction scheme?

The answers are apparently F and G, but I don't see why D and E couldn't also be valid (considering the first step is the slowest). A and B will inevitably be in the rate equation since they are ...
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0answers
20 views

Why does the molar conductivity decrease with increasing charge density?

This is a question in a problem sheet I have been set. Is it do do with the following equation: $\Lambda=\Lambda_0-a\sqrt c$? Surely charge density is proportional to concentration so therefore molar ...
3
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0answers
19 views

Will the Sulfur-Iodine cycle and Haber Method work at lower pressures and temperatures?

I have a yearlong research project next year in my senior year of high school in which we have to make some product or prototype to solve some issue. My interest was in the Liquid Fluoride Thorium ...
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1answer
52 views

Why do dianions (such as malonate) bind cations more strongly than anions?

Why does a dianion (such as malonate) bind cations more strongly than its equivalent anion (acetate)? Is it simply because of the proximal availability of another O- group that can bind to cations? ...
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1answer
49 views

How quickly does sulfur hexafluoride mix with the atmosphere?

A common science demonstration is to float a "boat" on sulfur hexafluoride. How long would the sulfur hexafluoride stay in the container (in the experiment linked above) if the container were to be ...
5
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1answer
63 views

When and why do hot material take heat from cold material?

This is what I read on Chemwiki: Rudolf Clausius was a German physicist, and he developed the Clausius statement, which says "Heat generally cannot flow spontaneously from a material at a lower ...
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25 views

The concentration is unity! Why? [duplicate]

I want to know why concentration of solids and liquids are taken unity in expression of equilibrium constant( heterogenous equilibrium). It is usually mentioned that the density of solids and liquids( ...
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1answer
37 views

Interaction between metalic nanoparticles and aggregation

I can't find any publication to deal with aggregation of colloidal metalic nanoparticles. What type of interaction(s) is/are there between aqeous metalic nanoparticles which give(s) rise to ...
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48 views

Abnormal termination of GAMESS in frequencies calculation

I want to optimize geometry and to analyse frequencies for transition metals ($\ce{Cu}$, $\ce{Mn}$, etc.) compounds using GAMESS. I use Avogadro for preparing input files and I have a problem: one of ...
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1answer
51 views

How to calculate valence factor (n-factor) for a element?

Suppose I am given some reaction in which $$\ce{C6H12O6 -> CO2}$$ and I want to calculate n-factor for this reaction to ultimately calculate equivalent weight of carbon for this reaction. Since ...
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2answers
31 views

Can I use my extech pH 60 meter to measure soil pH if so how?

Can I use my extech pH60 meter to measure soil pH if so how? I included a link to the meter. Extech pH 60
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1answer
970 views

Why is NaCl3 possible?

There. And there. Almost a year ago, a group of scientists claimed to have reached compounds of $\ce{Na}$ and $\ce{Cl}$ with weird stochiometries ($\ce{NaCl3, Na3Cl, NaCl7, Na3Cl2}$ and $\ce{Na2Cl}$). ...
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1answer
240 views

What chemicals help define “taste”?

As we all know that there are 5 tastes : sweet, sour, bitter, umami, salty. So what chemicals are there that help form these tastes, in other words how do our tastebuds experience these tastes? ...
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1answer
78 views

Difference between radial,planar,angular and spherical nodes

What is the difference between them ? I think radial nodes and spherical nodes mean the same. And angular and planar mean the same . Reference And finally how many spherical nodes are ...
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1answer
26 views

Order of priority in hybridization of d-orbitals

During hybridization of d-orbitals why the $d_{z^2}$ and $d_{x^2-y^2}$ orbitals are used up before the $d_{xy}$, $d_{yz}$ and $d_{zx}$ ?
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1answer
59 views

Why are C6 dispersion forces named C6?

I'm reading about water models and their dispersion coefficients, and going back to S. C. Wang's work according to the citation of an equation (Google books here) As you can see one citation's to a ...
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1answer
59 views

How to find partial pressures from a given equilibrium constant Kp?

I had following question on my quiz and but I answer it wrong because I can't seem to solve it. It is related to finding equilibrium constant. Question: For the following reaction, at ...