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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If dark surfaces absorb/store more light/energy than light surfaces, then does dark skin, on average, store energy from light most efficiently?

If darker surfaces absorb/store more light/energy per square inch than light surfaces, then does dark skin, on average, store energy more efficiently than light skin? (edited).
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Explaining Ionization to kids

I have a quest to explain a physical, chemical theory to kids of age 8-12. The topic is "Ionization". We all understand from early experiments of Physics and Chemistry (the Millikan oil drop ...
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959 views

Peroxide Linkages

Why are peroxide linkages generally weak? Is it due to Coulombic repulsions? I can't see how placing two oxygens with high degrees of partial negative character next to each other is a good thing in ...
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Nitrogen dioxide dimerization

$\ce{NO}$ can't dimerize and that is explained because the free electron is in an antibonding orbital. The same is true for $\ce{NO2}$, but it can dimerize, how?
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Why can't light pass through a gold foil, but alpha particles can?

Rutherfords experiment showed that most of the alpha particles passed through a thin gold foil undeflected. So why can't light pass through the foil, which is supposedly thinner than the heavy alpha ...
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How can two electrons lie together in an orbital?

Two electron of opposite spin can lie in a single orbital.. But what about the electron-electron repulsion. Okay! I got that the nuclear charge rather the large Z-effective overcome this repulsion by ...
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2answers
5k views

Difference between actual position of electron and Radial Distribution Probability

Its known that the radius of maximum probability of 2s orbitals is more than that of 2p orbitals. It means that the maximum probability of finding an electron in an 2s is further away from electron ...
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How to figure out which phase on a phase diagram will be the most dense?

If I am given a phase diagram, how can I determine which phase will have more density? What should I consider to solve these kinds of questions? Does the answer have to do with the area that each ...
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1answer
140 views

Proteins and their solubility

I have 2 statements , and i am not sure, whether they are true or false. Proteins like albumin and haemoglobin are insoluble in water (in my view , almost all proteins are soluble- so this is a ...
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1answer
113 views

What is the Solubility of Common Noble Gases in Concentrated Phosphoric Acid, 85% w/v?

By Henry’s Law, the concentration of a dissolving gas in a liquid is proportional to the partial pressure of that gas in contact with the liquid, mathematically, $ p = k_\mathrm{H} c$, where $p$ is ...
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1answer
185 views

Synthetical formation of diamonds

As everyone knows a diamond won't last forever. It will eventually turn into a graphite over a long period of time, as the free energy of graphite is lower than that of diamond, hence making the ...
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323 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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The highest melting point

Inspired by this question, what is the substance or compound with the highest melting point? At standard atmospheric pressure and ever-increasing temperature which substance a) eventually becomes ...
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68k views

How to calculate which ionic compound has the highest melting point?

Which of the following compounds has the highest melting point: $\ce{PCl5}$, $\ce{H2O}$, $\ce{NaCl}$, $\ce{SrCl2}$, $\ce{CaF2}$? In general, ionic compounds will have higher boiling points than those ...
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15k views

Is melting of gold a physical property?

I read that melting of gold is a physical property, but I wonder if this is true. If we want to melt gold we will need to add heat, and once we add heat to gold to melt it, there must be a chemical ...
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1answer
883 views

Corrosion of metals and observations in the agar medium?

I want to know which metals oxidize and which is reduced and changes in medium and observations? According to my knowledge more corrosion will take place in Zn and Fe also corrode. Then copper should ...
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4answers
28k views

What is the name of the formula ΔE = q + w?

What is the name of this formula? Google could not provide me with an answer. $$\Delta E=q+w$$
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2k views

Is sublimation a property of all substances?

I wonder if sublimation can be done only on certain substances like iodine, or it can be done on all substances. In other words, can sublimation be done, for example, on water? If it cannot, then why?...
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835 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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9k views

What are the fumes that form above liquid nitrogen?

What is the composition of liquid nitrogen fumes? Is direct contact with these fumes harmful?
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4k views

Finding orbit radius using the Bohr model and Rydberg equation

To start with its a homework problem, quite lengthy. A particle of mass equal to 208 times the mass of an electron moves in a circular orbit around a nucleus of charge $+3e$. Assuming the Bohr ...
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Advanced Level Chemistry Book Recommendation [duplicate]

I have a test comming up on Chemistry in Advanced Level and I sincerly ask for a book recommendation for chemistry. I already got the book chemistry by Ramond Chang. And I am pretty near to the exam. ...
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797 views

Is the E in Arrhenius equation the change of enthalpy?

I'd like to know whether the activation energy in Arrhenius equation is the enthalpy difference between the transition state and the reactant. If it's not enthalpy, is it Gibbs energy or something ...
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How can I determine the chemical composition of local rocks and minerals?

Specifically I live in the U.S. so I'm asking about an ordinary rock that you might find in your backyard or near a playground. Humans have discovered gun powder, petroleum, silica, iron, and many ...
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Acid-base equilibrium of NH4CN

I'm having difficulties understanding this problem. We have in the problem that $K_\mathrm a$ for $\ce{HCN} = 6.2\cdot10^{-10}$ and $K_\mathrm b$ for $\ce{NH3} = 1.8\cdot10^{-5}$. Write chemical ...
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4answers
922 views

On Heisenberg's uncertainty principle

Why can't we find the exact position and velocity of a particle? And why is it that if the uncertainty in position is very, very large then the velocity can be determined, and vice versa? Please ...
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Is there a reason for the mathematical form of the equilibrium constant? [duplicate]

Why are the two molarities multiplied and not added, and why is each raised to the power of the coefficient rather than multiplied by it? What is the reasoning behind this form? Was it simply ...
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How to use molality and molarity to determine the molar mass of a compound?

An aqueous solution of a certain organic compound has a density of $1.063~\mathrm{g/mL}$, an osmotic pressure of $12.16~\mathrm{atm}$ at $25.0~\mathrm{^\circ{}C}$, and a freezing point of $-1.03~\...
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448 views

Why is up spin in the px orbital and down spin in the py orbital considered an excited state? [duplicate]

Why is this form of p orbital occupation an excited state? I understand that there should be one up spin and one down spin in one orbital box by Pauli's exclusion rule. But in the p orbitals, it doesn'...
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1answer
2k views

Difference between torsion, out of plane, coplanar and perpendicular bends?

In Infrared spectroscopy, stretches are easily understandable. But, how do I visualize (or conceptually understand) the difference between dihedral (torsions), out of plane bends, coplanar bends, and ...
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146 views

How do I find out if ions are oxidised/ reduced based on half cell potentials? [closed]

Assuming standard conditions, answer the following questions. (yes/no) Is $\ce{Fe^{2+}(aq)}$ capable of reducing $\ce{Cr^{3+}(aq)}$ to $\ce{Cr^{2+}(aq)}$? Is $\ce{Sn^{2+}(aq)}$ capable of ...
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1answer
781 views

Electric field effect on reactions

What would be the effect of putting a solution in a strong electric field? Would the reactions in the solution be affected? I'm thinking yes – lots (if not all) – chemistry is dependent on charge (...
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1answer
355 views

Entropy - “Wiggle”?

The title is not a reference to a Jason Derulo song. In any case: 1) How is change in entropy measured, experimentally? I've Googled this for a bit and I've found all sorts of mathematical ...
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182 views

Hosoya Z Index and Correlation with Boiling Point

I have recently read about the Z topological index found by Hosoya. The papers/sources The Z index is the sum of the coefficients of the matching polynomials (no. of ways to choose an independent edge ...
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2answers
907 views

Evaporation of water

What are the conditions for the evaporation of water? I know that for the boiling of water, the vapor pressure of water must equal the partial pressure of water vapor. But what about for ...
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1answer
423 views

How to obtain product ratio from energy differences via Boltzmann statistics

I am currently calculating some reactions and I would like to express the ratio of the products in per cents. I am using the Boltzmann statistic in the following way: The probability $p_j$ of a ...
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1answer
336 views

How to find the potential of a mixed Iron/ Cer solution?

Given the following half-reactions: \begin{align} \ce{Ce^{4+} + e^{−} &-> Ce^{3+}} & E° &= 1.72~\mathrm{V}\\ \ce{Fe^{3+} + e^{−} &-> Fe^{2+}} & E° &= 0.771~\...
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1k views

Find the color of the solution

The acid-base indicator methyl red has a $K_{a}$ = $1 \times 10^{-5}$. Its acidic form is red while its alkaline form is yellow. If methyl red is added in a colorless solution with a $pH = 7$, the ...
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1answer
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When is it true that more nodes equals higher energy?

Consider all the MOs of some isolated molecule. (It could be a single atom too; I'll use MO to refer to AOs as well.) Number them in increasing order of the number of nodes (node = surface where the ...
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409 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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3answers
527 views

What does the hydrolysis of a salt tell us about its basic/acidic character?

I'm curious to know how basicity and acidity arises when a salt or covalent compound is dissolved in water.
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1answer
198 views

What stable arrangements of hydrogen-bonded water exist in the range of 4-20 water molecules?

Water clusters made up of various numbers of water molecules have been described. Are all of these structures theoretical? What experimental evidence supports any of these structures? How does the ...
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2answers
860 views

Bombarding atoms with electron gun?

Just to explain this question in a better way just think about the Rutherford's experiment(the alpha particle bombarded on Gold foil) be conducted using a electron gun in place of the Alpha one.. So ...
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0answers
54 views

Other than heating, is there any evidence that normal RF radiation (say, microwave range) can affect chemical reactions?

There's been a lot written (and debunked) about alleged biological effects from RF radiation, even when it's too low powered to cause heating effects or ionization. Is there any chemical reason to ...
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1answer
933 views

how are the frequencies at a local maximum of PES like?

On the potential energy surface, if you find a local maximum and calculate its frequencies in Gaussian or something like that, will you get all negative frequencies or all positive frequencies? I know ...
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2answers
84k views

Is there an easy way to remember charges on ions?

I have a chemistry test coming up and I might need to know the charge that goes with the different ions like $\ce{SO4}$ has $-2$, $\ce{NO2}$ is $-1$ and $\ce{PO4}$ is $-3$. Is there an easy way to ...
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1answer
886 views

Wavelength of X-rays

What will be the wavelength of X-ray if we apply a potential difference of , say 20 KV across the ends of the x-ray tube ? Alright, i started with the modified de-broglie equation $$\Lambda=\frac{h}{\...
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1answer
5k views

How to dissolve grass/leaves without affecting enclosure?

I've got two questions: What sort of compound can dissolve grass/leaves fastest without leaving "much" trace? What sort of enclosure is required for this to be doen safely and without damaging the ...
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1answer
168 views

Sign of the work done during a reversible compression

The work done during a reversible compression - if $V_\mathrm{i} = V_1$ (initial) and $V_\mathrm{f} = \frac{1}{6}V_1$ (final) - of an ideal gas is? I chose $1.8 p_1 V_1$. Is it right or should it be $...
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4answers
14k views

Why is the enthalpy of vaporization greater than the enthalpy of fusion?

Why is the molar enthalpy of vaporization of a substance larger than its molar enthalpy of fusion (at constant pressure); for example, in the case of ice and water.