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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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Thermodynamics and thermo chemistry [on hold]

Explain Enthalpy concept and about how to calculate heat of neutralization, bond energy, combustion etc
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0answers
14 views

Chemical Formula [on hold]

Nitrogen forms a number of compounds with oxygen, for example nitrous oxide, N2O, is 63.65% N by mass. A second compound, which contains two atoms of nitrogen per molecule, is 25.94 % N by mass.How ...
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1answer
53 views

Lattice energy of NaCl and MgCl

In an exam paper it says that the lattice energy of NaCl is more exothermic than MgCl as the Na+ cation has a smaller ionic radius than Mg+. Here are the resources given: What is the reasoning for ...
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1answer
25 views

Can an uncharged particle pass through a molecular bond? [on hold]

Do particles ever pass through or interact with the molecular bond? Is there a physical size limit? What happens to the atoms and the particle and does this ever happen in real life?
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0answers
11 views

how do measure Calorific value of coal by bomb calorimeter? [on hold]

i use isoperibol mode of calorimeter to find calorific value of coal sample but when i change mode to dynamic ,the result is higher than isoperibol ...why ? and what is difference between isoperibol ...
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1answer
25 views

How do you figure out fuel specific impulse non-experimentally?

Simple question, probably very complicated answer: Without building a test engine/rocket and finding out experimentally, that is to say, based on chemical characteristics alone, how can one compute ...
-2
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0answers
23 views

Determine molecular weight when only mass volatilizes

I'm just gonna go straight to the point. I can't find a solution to this problem. Before I start I must say that I don't remember exactly what the problem states but this is pretty much it: 200  g ...
-1
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0answers
43 views

physical chemistry [on hold]

Consider neon as ideal gas with a Maxwell distribution of speeds. (a) For Ne at T = 300 K, obtain median speed vmed such that fractions of molecules with speeds above and under this value are equal. ...
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1answer
29 views

Why it the electron affinity of beryllium is greater than nitrogen? [on hold]

As we know that fully filled electronic configuration is more stable than half filled electronic configuration, so in my opinion beryllium's electron affinity should be less than nitrogen's. Is my ...
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1answer
47 views

Effective attenuation coefficient for polychromatic light

The Beer-Lambert law gives the optical intensity of collimated light as a function of depth $z$ as: $$I(z)=I_{0}\mathrm e^{-\gamma z},$$ where $\gamma = \alpha + \beta$ is the wavelength-dependent ...
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0answers
35 views

How is Be(OH)4 Formed?

I recently did a test paper and the question stated that Be(OH)2 is amphoteric and so I was asked to write equations showing it both acting as an acid and a base. Acid answer: $\quad\ce{Be(OH)2 + 2H+...
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1answer
30 views

Preparation of Heavy water [closed]

In electrolysis of normal water, why does adding some NaOH and electrolysing the water leave D2O behind ?
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1answer
36 views

Why are diagonal arrows disallowed in Jablonski diagrams? [on hold]

My professor mentioned in one of our lectures that diagonal arrows in a Jablonski diagram are disallowed. As far as I know, horizontal arrows signify conservation of energy, while vertical arrows ...
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1answer
34 views

What about Miller Indices of planes passing through origin?

For Miller Indices of planes if we encounter a case where the plane passes through the origin then I have heard that the only remedy can be arrived by shifting the origin to a different point.However ...
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0answers
14 views

what the probability of finding a particle in the first quadrant and a 2d box? [closed]

What the probability of finding a particle in the first quadrant and a 2d box? What is the expression for this? I thought that it would be 1/4 as there are 4 quadrants, but is this incorrect?
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1answer
23 views

Transition levels in Balmer series

When we talk about second line of Balmer series, from which energy level to which energy level transition are we talking about?
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1answer
27 views

Question About Ion Identification Chemistry Help

For the reactions shown below, we added 5.00 mL of 0.0390 M $\ce{NaOH}$ to a test tube containing one of the two cations ($\ce{Ni^2+}$ or $\ce{Fe^3+}$) and recovered 0.00695 g of precipitate. $$\ce{...
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1answer
14 views

Calculation of rate law for multi step reaction [closed]

Please help me to solve this one. I'm having a bit of a hard time grasping these concepts.
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1answer
66 views

How is silver chloride more soluble in brine than water?

I heard that: Silver chloride is more soluble in very concentrated NaCl solution (brine) than in pure water. Is it true? I mean won't the common ion effect operate? Or may be this is due to some ...
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0answers
25 views

How much urea will separate out?

I have a question of solution chapter and I m having problem in both in solving as well as understanding that problem . The problem is: "One hundred grams of a $\pu{5m}$ urea solution is cooled to $...
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0answers
29 views

Seeming discrepancy between pKa and corresponding Ka of methylamine

The first entry in PubChem for the $\mathrm pK_\mathrm a$ of methylamine is $10.657$ at $25\ \mathrm{^\circ C}$. My elementary understanding is that this would be found as the negative log of the $K_\...
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0answers
41 views

Specific heat of water question

I'm working on a problem and am unsure how to proceed past the first step. If 30 grams of water at 10 C are added to 180 grams of ice at -110 C (assume the cup is insulated) what is the final ...
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0answers
21 views

What is really meant by a charge? [duplicate]

What is the major difference between formal charge and the oxidation or reduction state of elements?
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0answers
17 views

Why are Txy diagrams curved for dew point and bubble point?

What is the reason behind drawing dew point curve and bubble point curve as curved (and dew point curved outwards and bubble point curved inwards) for Temperature vs Composition Phase Diagram as per ...
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0answers
43 views

Calculation of average bond length from force constant and IR absorption?

I need some help beginning a problem set problem (just want hints, I'd like to figure it out myself). The problem gives me the IR absorption for a diatomic, as well as the force constant for the ...
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0answers
31 views

Number of octahedral and tetrahedral voids present in a HCP structure

The given image depicts the tetrahedral and octahedral voids in HCP structure. For the tetrahedral part I figured out that there would be 6 tetrahedral voids in total. My visualisation: In the ...
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1answer
35 views

Why is the equilibrium constant unaffected by a change of the initial concentration?

In my class, it was taught that the equilibrium constant does not vary with the intial concentration of the reactants? Why is it so?
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0answers
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To which all factors chemical equilibrium is directly proportional to? [closed]

The equilibrium constant is directly proportional to the concentration. why it is so? Is chemical equilibrium dependent on temperature and other such factors? Then why we only focus on concentration?
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0answers
52 views

What bonding allows chloroaluminate (AlCl4-) to form?

How is $\ce{AlCl4-}$ formed when $\ce{Al}$ only has $3$ electrons in it's outershell. It would be able to give $3$ electrons away with $\ce{AlCl3}$ for it to have a full outershell but how does it ...
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1answer
31 views

Solve for wavelength of photon given threshold frequency

The threshold frequency of a potassium metal plate is $\pu{4.35\times10^14 Hz}$. Determine the wavelength of a photon required to reach $\pu{2.50 eV}$ of the maximum kinetic energy of an emitted ...
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0answers
34 views

Comparing pressure and volumes of ideal and real gas

This question has been troubling me for quite a while now. Which has greater pressure: Real gas or an ideal gas under similar conditions? What about their volumes? I read this in many sources and ...
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2answers
42 views

Calculate Rate constant, k, for a consecutive reaction where k1<<k2

I have a consecutive reaction where the first step is the rate determining step so $k_1<<k_2$: $$\ce{A ->[$k_1$] B ->[$k_2$] C}$$ The rate law can be shown to be: $$[\ce{C}] = {1 - \exp(...
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0answers
16 views

Reference Request - An Intuitive Approach to Chemistry [duplicate]

I am looking for a book on general chemistry that explains the theories. For example, it may start out with talking about chemistry before the molecular theory (such as the conservation of mass and ...
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2answers
40 views

Whether for all zero order reactions rate is independent of concentration of reactants

For example,for the reaction $\ce{A + B \longrightarrow C}$,If rate law expression is: $$\mathrm{Rate=k \times [A]^{(0.5)}\times [B]^{(-0.5)}}$$ It is a zero order reaction but whether it is ...
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0answers
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What is electron affinity? [duplicate]

In some books, I see electron affinity is the amount of energy released, when an atom gains electron whereas in others books it is written that electron affinity is the change in energy of the atom ...
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1answer
36 views

Why do inert gas have zero electron affinity? [closed]

As we know, we have to apply large amount of energy to cause an inert atom lose electron, so in that case, shouldn't its electron affinity be negative?
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1answer
49 views

Expansion work by a gas when pressure is not explicitly constant?

How is it possible to calculate the work done by a gas when pressure is not explicitly stated to be constant? The question states: Calculate $\Delta H$, $Q$, and $W$ when $1\ \mathrm{mol}$ of He ...
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0answers
41 views

How to without calculations understand the liquid-liquid extraction efficiency?

I'm asking myself this question for a very long time and I haven't found a simple an good explanation yet for the fact that it's better (if you want to clean them) to wash your hands two times with ...
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1answer
59 views

Does a molecule need to be placed symmetrically in the unit cell?

I was watching an OCW by MIT (3.091X) on solid state. My previous notion of lattice point and unit cell got shattered after this example. Where are the unit cell and lattice points in this picture? ...
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1answer
440 views

Why do different gases have the same molar volume?

Molar volume: The molar volume, symbol $V_\mathrm m$ is the volume occupied by one mole of a substance (chemical element or chemical compound) at a given temperature and pressure. At S.T.P ...
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1answer
100 views

should charge balance be based on activities?

We have a fluid with $\pu{0.01 M}~\ce{HCl}$ and $\pu{0.02 M}~\ce{K2HPO4}$, so if we assume activity coefficients are $1$ throughout we can find pH as $6.800012$ and confirm that at that pH there is ...
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1answer
52 views

Maximum Concentration of Benzene possible

A question for my PhysOrg course states: Assume you are performing a reaction in which benzene is a reagent. What is the maximum concentration of benzene possible? Hint: what facts do you need to ...
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1answer
48 views

Why do the 4f and 5d orbitals have similar energies?

I've come to know this phenomena when learning about the exceptions to the aufbau principle. But there is no explanation of why 4f and 5d have similar energies (as I've read in some websites).
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1answer
38 views

PCl3 vs SCl2 boiling point

Why does sulfur dichloride have a lower boiling point than phosphorus trichloride? Is it to do with the higher number of electrons causing stronger id-id interactions in PCl3, or do we need to compare ...
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0answers
41 views

Planck's Distribution Over a Range of Wavelengths

I am taking PChem this semester and I am stuck on this problem. Calculate the energy density in the range $\pu{650 nm}$ to $\pu{655 nm}$ inside a cavity at (a) $\pu{25 ^\circ C}$, (b) $\pu{3000 ^\...
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0answers
37 views

Lennard Jones Potential - Water

I am trying to code the Lennard Jones potential (LJP) for water (reproducing results in a paper). The paper reports epsilon and sigma values for Oxygen and Hydrogen separately but in the LJP I've been ...
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1answer
71 views

How many equal Xe–O bond length are present in (XeO_6)-3? [closed]

I tried to solve this problem by drawing a structure but the structure did not give me any answer and I was not able to draw the proper structure please help me out.
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1answer
39 views

Rate of a reaction [duplicate]

We know that the rate of a reaction $\ce{aA + bB -> cC + dD}$, the rate of the forward reaction is given by $r_\mathrm f = k_\mathrm f[\ce A]^p[\ce B]^q$ where $ a\neq p$ and $ b\neq q$ according ...
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1answer
16 views

Molarity of a substance in a solution when more fraction is given

Mole fraction of ethanol in a solution with water is $0.040$. What will be the molarity of ethanol in water? Density of water can be assumed to be $1\ \mathrm{g/mL}$. This is how I tackled the ...
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1answer
76 views

How are the LCAO ansatz and Slater determinant ansatz for the wavefunction connected?

Say we have a system of 2 electrons, an ansatz for the wavefunction is then a Slater determinant consisting of two orbitals. $$ \left|\Psi_{Slater}\right>= \frac{1}{\sqrt{2!}}\left(\left|\phi_1\...