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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Why do liquid crystal displays (LCDs) visually distort under pressure?

A venerable question, as old as LCDs themselves. I assume it has something to do with pressure-induced changes in the path length across the display, but that's just a guess. Of particular interest to ...
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A function for getting the nuclide's nuclear binding energy?

Is there a function $f(A)$ or $f(Z, A)$ that gets the energy of nuclear binding of one nuclide in atom? Or other way to get it? My chemistry book says only to get it from the chart which is very ...
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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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947 views

The molar mass of aluminum by measuring the amount of hydrogen gas liberated when a sample of aluminum is treated with excess hydrochloric acid

This experiment involves the determination of the molar mass of aluminum by measuring the amount of hydrogen gas liberated when a sample of aluminum is treated with excess hydrochloric acid. In the ...
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What does HTO decay into?

I'm aware that tritium undergoes beta decay forming Helium-3. But in the case of HTO, what does it decay into? I don't suppose it decays into HeHO.
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Why does MgCl2 lower the freezing temperature, and how does it do so?

I am working on a project in my chemistry class, and even though we've already finished the lab, I'm still confused as to why and how $\ce{MgCl2}$ melts ice/ lowers the freezing temperature of water. ...
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Why does water dissociate to H3O+ and OH- rather than H+ and OH-?

Why does water dissociate to $\ce{H_{3}O^{+} + OH^{-}}$ instead of $\ce{H^{+} + OH^{-}}$? This question came to surface when I was learning about acids and bases, and learned this definition: $\...
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557 views

What is the solid crud that appears inside my kettle?

Almost every share-house I've lived in has had some nasty looking solids collecting inside. I always regret looking inside the kettle because a cup of tea never tastes quite as good after you've seen ...
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Is there a element that shows this pattern of boiling point?

Is there a compound that turns to gas at a certain temperature but if heated more turns back to liquid and if heated more than turn to gas? Does it exist naturally? Has a such a substance be found? ...
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Calculation of Atomic weight percentage in AAS

I am currently doing doping studies in a system similar to this ($\ce{A_{x}B_{1-x}}$) and I have to find atomic weight percentage of $\ce{B}$ element using atomic absorption spectroscopy(AAS). I have ...
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Why sponge can't absorb mercury

Recently I have watched a video demonstration with a sponge and mercury and the sponge can't absorb mercury like it does with water. Why is that?
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Why are the total energies of transition states so commonly corrected for zero-point vibrational energy?

So often I see total energies of transition states corrected for zero-point vibrational energy which always confuses me. Zero point energy is the lowest energy that a ground state minimum energy ...
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How effectively bound Na2CO3 and BaCL2 water

How fast does $\ce{BaCl2}$ bind water from its surroundings, becoming a hydrate, compared with same process with $\ce{Na2CO3}$?
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How can enzyme/substrate reactions that adhere (largely) to quantum theory also require 'Newtonian' consideration of gravity?

I'd just like to ask for a little clarification here due to confusion from interdisciplinary studies. I'm currently reading the 1976 paper related to the recent 2013 Nobel Prize for Chemistry, by 2 ...
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Heat Capacity and Calorimetry

Why does the heat capacity of a calorimeter, C(cal), need to be determined? A calorimeter contains 50.0 mL of water; both are at 21.2 degrees C. Then the 50.0 mL of water at 57.6 degrees C is added ...
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Do acids without hydrogen taste sour?

I have heard that acids taste sour because of hydrogen (I don't really know exactly). According to the definition of acids: An acid (from the Latin acidus/acēre meaning sour) is a chemical ...
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What Does the Equilibrium Constant represent? [duplicate]

If the Equilibrium constant stands for the extent of reaction at equilibrium, whether more of forward or backward reaction is taking place, then why is it not affected by factors like concentration of ...
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How do point defects in a crystal relate to Entropy?

I am interested in Non-Stoichiometry and how it relates to crystal structures; In particular I wish to learn about surfaces of metal oxides. I am aware that point defects in such crystals are a result ...
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Strange observation!

Every one have observed that when we pour cool water into a transparent glass (or simply glass), some droplets accumulate on the outside part. Did the droplets come pass through the glass? If they ...
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Attempting to balance a redox reaction using half reactions leaves an unbalanced component

I have this redox reaction that I can't balance using half reaction method. $$\ce{Mg + HNO3 -> Mg(NO3)2 + N2O + H2O}$$ What I get at the end is $$\ce{2Mg + 6HNO3 -> 2Mg(NO3)2 + 3N2O +3H2O}$$...
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Solvated solids

I have a very basic question concerning solvation. If a solid (solute) was dissolved in a liquid (solvent), is the solute still in the solid state? or does it convert into another state of matter when ...
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How exactly is activation energy defined?

In a common interpretation of the Arrhenius rate equation $$k = A\exp\left(-\frac{E_\mathrm a}{RT}\right),$$ the activation energy $E_\mathrm a$ is understood to represent the difference in the ...
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Stoichiometric defects in silver bromide

Stoichiometric defects (Schottky and Frenkel defects) in ionic crystals are formed due to irregularities in the ionic arrangement which maintain the stoichiometry and electroneutrality of the solid. ...
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How to detect H₂SO₄ (aq) and NH₃

We have two bottle named $\ce{H2SO4~(aq)}$ and solution of $\ce{NH3}$ but we don't know their name actually. What I have to do to detect these solution by only using : $\ce{CuCl2}$ or $\...
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Is it possible to save an insoluble snowflake?

In The Big Bang Theory Season 3 Episode 1 "The Electric Can Opener Fluctuation" Leonard gives Penny a snowflake that will never melt. He said some type of chemical gas name when he try to explain, ...
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Why was anhydrous magnesium carbonate “upsalite” discovered so late?

What complicated the synthesis of upsalite (anhydrous $\ce{MgCO3}$), for it to be synthesized and published in 2013 as opposed to the 20th century, as one would expect for such a simple salt?
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How to calculate the probability of finding an electron in a box between 0.25L and 0.75L?

If the wavefunction of the electron in a box of length $L$ is $$\psi{(x)}=\sqrt{\frac{2}{L}}\cdot\sin{\frac{n\pi x}{L}}$$ What would be the probability of finding the electron between $0.25L$ and $0....
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Clarifications on thermodynamic cell efficiency

The thermodynamic efficiency of any cell (especially Fuel cells) is given as $$\frac{\Delta G}{\Delta H} \times 100$$ I understood this partly, that since $\Delta G$ is the useful work obtained in ...
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Is sublimation caused by an environmental difference or an element's composition?

I was having a conversation when the topic of sublimation came up. Prior to the discussion, I had always thought that sublimation was caused by a great pressure/temperature difference, but another ...
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Nuclear fusion reactions violate law of conservation of mass, but it has not yet been taken into account. Why?

According to the law of conservation of mass, during any physical or chemical changes, the total mass of the products is equal to the total mass of the reactants. But in nuclear fusion reaction if ...
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The ionization energy of H₂⁺ molecule ion

I am trying to compute the ionization energy of $\ce{H2+}$ molecule ion from the electronic energy spectrum. The question is whether one should use the purely electronic Hamiltonian or the Hamiltonian ...
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Why are sigma bonds stronger than pi bonds?

Why are sigma bonds stronger than pi bonds?
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What is advantage of creating elements that disappear in a flash?

More than dozen of heavy elements of periodic table do not occur naturally but are prepared artificially at nuclear reactors.. These elements are said to disappear in a flash.. So, why invest lot of ...
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Find the number of copper spheres in a box

A box contains a mixture of small copper spheres and small lead spheres. The total volume of both metals is measured by the displacement of water to be $\pu{420 cm^3}$ and the total mass is $\pu{5.4 ...
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Calculating standard enthalpy of reaction, which reactant to choose for the amount of substance

For example, this reaction: $$\ce{2NaOH + H2SO4 -> Na2SO4 + H2O}$$ Suppose both concentrations are $1\ \mathrm{mol\ l^{-1}}$ (standard condition). There is $0.02\ \mathrm{mol}$ ($20\ \mathrm{cm^3}$...
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Transition state and free energy

We have products $\ce{A + B}$ combining to form $\ce{C + D}$ through the transition state $\ce{X}$. Are all reactions at least virtually reversible? Is the difference between a reversible reaction ...
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Prediction of ionic reduction?

Here are some standard electrode potentials:- $$\ce{SO_4^{2-} + 4H^+ + 2e^- -> SO_2 + 2H_2O}\\E^o=0.17\mathrm{V}\\ \ce{NO_3^- + 4H^+ + 3e^- -> NO + 2H_2O}\\E^o=0.97\mathrm{V}\\ \ce{NO_3^- + ...
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Superheating metal alloy above solidus

Is it possible to heat a material above its solidus without melting occurring? More specifically, at a heating rate of approximately 200K/s, will a metal alloy exhibit superheating and if so by what ...
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Is the current situation possible for recreaction in a lab?

I want to convert cellulose to another form (crystalline => amorphous). Cellulose requires a temperature of 320 °C and pressure of 25 MPa to become amorphous in water.(Is the pressure achievable in ...
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886 views

Why is water evaporation not more commonly used to cool buildings [closed]

Water has a very high heat of vaporization (2260 kJ per kg). Why not just gradually sprinkle water on your roof to keep the building cool in opposed to using air conditioners? It wouldn't take much ...
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Express the maximum work from a voltaic cell

The net cell reaction of an electrochemical cell and its standard potential is given below: $$\ce{ Mg + 2Ag+ ->Mg^{2+} + 2Ag} \ \ \ \ \ \ \ \ E^\circ=3.17\:\mathrm{V}$$ The question is to find the ...
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Which elements have no liquid form at atmospheric pressure?

Carbon has no liquid form at atmospheric pressure. Is this unique amongst naturally occurring elements? The more interesting and vague question is, is this property somehow important or related to ...
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What is known about liquid carbon?

The wiki tells me that if you heat carbon at atmospheric pressure it eventually turns directly into a gas without being liquid first. At what pressure can you make liquid carbon? Has anyone actually ...
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If the pH is zero, what would be the normality of a sulphuric acid solution?

If pH of the solution is zero, what would be the normality of $250 \, \mathrm{ml}$ $\ce{H2SO4}$ solution? My work: $\mathrm{pH} = 0$, hence the concentration of $\ce{H+}$ ions is $\pu{1 mol L^-1}$, ...
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Why search new elements?

I've read this today. From the little I know, they discover new elements by bombarding some atoms in particle accelerators (I guess) and these new elements last a few miliseconds. So what's the ...
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Is there any relationship between ultrasonication and temperature

In chemistry we use ultrasonication for cleaning vessels ,synthesis of chemical compounds (sonochemistry) etc.I know that during ultrasonication high temperature and pressure is formed "locally".But I ...
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Thermodynamics behind Deliquescence?

The phenomenon of deliquescence wherein a water soluble substance absorbs water from atmosphere and dissolve in it forming a saturated solution, has thermodynamic roots. I have read the fact that the ...
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Entropy and enthalpy change on mixing liquids

Question: A concentrated solution of copper sulphate, which is dark blue in colour, is mixed at room temperature with a dilute solution of copper sulphate, which is light blue. For this process: ...
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Identifying the gas given ratio of its specific heats

The ratio of the heat capacities $\frac{C_\mathrm p}{C_\mathrm v}$ for one mole of a gas is $1.67$. The gas is: a) $\ce{He}$ b) $\ce{H2}$ c) $\ce{CO2}$ d) $\ce{CH4}$ I know how to answer ...
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Storing kinetic energy in bonds

Let's assume a setup with a static linear molecule with three identical atoms connected by bonds and a single atom, identical to the other three, being shot at the molecule. Let's also assume that ...