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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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46 views

Theoretical Calculations for Potential Generated in Salt Water Battery

I am using a $\pu{1.5 M}~\ce{KCl}$ solution as electrolyte and copper and aluminium electrodes but no salt bridge. So basically there is only one beaker with the two electrodes in it with the $\pu{1.5 ...
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76 views

Adiabatic flame temperature of a blast furnace gas

Calculate the adiabatic flame temperature of combustion of a blast furnace gas analyzing $25\%$ $\ce{CO}$, $10\%$ $\ce{CO2}$, and rest nitrogen. Use theoretical amount of preheated air at $\pu{1000 °C}...
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25 views

3D printing of alumina

I want to print a structure of alumina, and the 3D printer that I am using is an extrusion-based printer. So I need your help in knowing that what composition (binders and deflocculant) of alumina ...
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51 views

Can a substance be extracted from solution by adding another substance with a higher solubility?

Suppose that I have a substance X dissolved in water. I then add a substance Y to the solution. Substance Y has a higher solubility in water than substance X, and more than enough of substance Y is ...
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34 views

Deriving the entropy as a function of concentration

In a physical chemistry class, the professor derived entropy $S$ as a function of concentration starting from $S=k\ln(W)$. Somehow he made a mistake and ended up with the wrong sign. This remains ...
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17 views

In dS≥dQ/T, material equilibrium means that there is not material changes at all or that a material change can be reversible and at equilibrium?

I am reading Levine's Physical Chemistry, I know how to arrive to that equation, but I have questions. First, $\mathrm{d}S=\mathrm{d}Q/T$ for material equilibrium, but if there is a heat flow I ...
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48 views

First Order Chemical Kinetics

I have the following system of reactions: \begin{align} M & \xrightarrow{\lambda(M,W)}M+M \\ W & \xrightarrow{\lambda(M,W)}W+W \\ M & \xrightarrow{\mu} \emptyset \\ W & \xrightarrow{\...
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38 views

Why has na 1S0 term Ag symmetry?

This question is a continuation of Molpro - Connection between atomic term symbols and system symmetry. In the Feodoran's answer I found it somehow confusing, that ${}^1S_0$ term should be totally ...
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64 views

Significance of this unusual matrix element

Recently, I was solving some questions on Rigid Rotor. I found this question very amusing. Evaluate the integral i) <$Y_{l,m+2}$ | $L_{x}^{2}$ | $Y_{l,m}$ > I evaluated it, found that the value ...
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60 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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86 views

distillation of aqueous CAN solution for the purpose of a reversible and strong endothermic reaction in cool packs

I know calcium ammonium nitrate (CAN) is used for cold packs. By bending a small metal plate the salt gets dissolved in water (separated pack) and this process is endothermic. I would like to heat ...
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156 views

Why do we neglect the zero point energy in statistical mechanics?

Quantisation associated with translational modes can be modelled like a particle in a box (PiB). $$E_n = \frac{n^2h^2}{8mL^2} \qquad n \in \mathbb{Z} \, | \, n \ge 1$$ By the equation above, the ...
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198 views

Numerical related to crystallisation of water below its freezing point

Question: There is $16\ \mathrm g$ of pure water in a container at temperature $-20\ \mathrm{^\circ C}$. A small piece of ice is added to start crystallization. Amount of water in container when ...
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39 views

Subtracting conductivities?

I don't understand why the conductivity of water is relevant here? After converting everything to si units Why can't we simply divide the given conductivity of aq agcl by x and equate that to the ...
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204 views

Why doesn't a temperature and pressure gradient exist in a container of real gas?

In the Kinetic theory of gases, it is assumed that there are no intermolecular forces between the atoms/molecules. But real gases, have intermolecular attractive and repulsive forces. Suppose a ...
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141 views

Boiling points of Hydroxylamine and water

Why does $\ce{NH2OH}$ have a lower boiling point than water? According to Wikipedia, hydroxyamine has a boiling point of 58 °C. Could this be due to the extent of hydrogen bonding among both molecules?...
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47 views

Can Water Oxidize Cu(I) to Cu(II)

Is DI water (also without $\ce{O2}$ gas dissolved in it after degasification) a sufficiently strong oxidizer to oxidize $\ce{Cu(I)}$ in $\ce{Cu2O}$ to $\ce{Cu(II)}$ forming $\ce{CuO}$? Will this ...
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46 views

Change in total gas pressure

The question reads: For the part were they ask about the total gas pressure, would it be correct to say that the total gas pressure doesn't change? Instead of $0.8$ $atm$ of $N_2O$, it is now $0.8$ $...
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124 views

How does Le Chatelier's principle apply to a fuel tank full of hydrogen?

A nano-tube packed fuel tank is full of Hydrogen, and there is a steady pressure of Hydrogen in the tank. While hydrogen gas is being removed from the fuel tank to power the car, the pressure in the ...
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3k views

Which of these functional groups is soluble in aqueous HCl and/or NaOH?

http://pastpapers.papacambridge.com/view.php?id=Cambridge%20International%20Examinations%20%28CIE%29/AS%20and%20A%20Level/Chemistry%20%289701%29/2015%20Jun/9701_s15_qp_42.pdf I need some help to ...
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337 views

Can final volume differ from initial volume in a constant volume process?

A sample of 1.00 mol perfect gas molecules with $C_{p,\mathrm m} = 7R/2$ is put through the following cycle: (a) constant-volume heating to twice its initial volume, ... (Problem 2.5, Atkins Physical ...
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90 views

Will OH- ions be reduced or H+ ions be reduced in KOH electrolyte

I was trying to see if I can make a battery that uses KOH as the cathode electrolyte with platinum as the cathode electrode, but I got confused as to what gets reduced in this solution (Aluminum ...
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2k views

Why do we measure the initial rate of a reaction?

Why do scientists usually measure the initial rate of a reaction, instead of measuring the rate some time into the reaction?
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143 views

If fluorine and cerium ion have more oxidising power than KMnO4, why is KMnO4 more popularly used as an oxidising agent?

It is quite clear from the electrode potential values that $\ce{F2}$ and $\ce{Ce^{4+}}$ are better oxidizing agents that $\ce{KMnO4}$.
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55 views

What criteria based on expressing standard rate of reaction?

When given the reaction: $\ce{NO2}$ reacts with $\ce{O2}$ to produce $\ce{N2O5}$, how do I calculate the rate of consumption of $\ce{NO2}$ when the rate of the reaction= 0.02 M/s? I am confused ...
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26 views

Finding the binding energy iof methylated miRNA to an mRNA

I'm working on a project in biophysics and I need to find if there is a difference in binding of an miRNA to an mRNA when in one case the miRNA is methylated and in the other it isn't. What tools ...
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23 views

Before going into stable states ( i.e less energy states ) , do exothermic systems become unstable for a short time on the basis of Kinetic Energy?

In most of the cases the reactions are exothermic because all systems want to reduce their net energy and one way to do that is by loosing the $KE$ of the molecules to the surrounding molecules by ...
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2k views

Steric factors greater than 1 or less than 0?

From my understanding, the steric factor accounts for the relative orientation required by reactants in order to react in collision theory. This implies that steric factors should probably always be ...
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443 views

Deriving the volumetric thermal expansion coefficient from other properties?

I have a lot of gas properties in a model but I discovered that he volumetric thermal expansion coefficient is not among them. I've found little about how the constant relates to other properties - I ...
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63 views

Boiling Point Reversal

If substance A boils at a lower Temperature than substance B under atm. pressure, can it be that under some other condition, say, elevated Pressure or under vacuum a reversal of the trend occurs? i.e....
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104 views

What causes mercury to expand equaly unregarded what the temperature increase is?

Mercury seemed to be a good liquid to use in thermometers. But why are most liquids expanding non-linearly with increase of temperature compared to other liquids?
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40 views

Wetting properties of FTO coated glass

I am trying to spin coat a layer of polymer+Quantum Dots on an FTO coated glass slide. My material is forming agglomerates at the edges of my slide. My polymer is PVK which has a conc of$\approx 4.5mg/...
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69 views

Type of adsorption in catalysis

why type of adsorption takes place during catalysis? It can't be physisorption because it involves formation of chemical bond. It shouldn't be chemisorption too because it is characterised by ...
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2k views

What exactly happens at the critical solution temperature of a phenol water system?

What makes phenol that was turbid go clear beyond the critical solution temperature? We say beyond the critical solution temperature the constituents become soluble. What is the reaction or the exact ...
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25 views

How to sequester Na+ which prohibits the formation of a micro-emulsion in solution

I am mixing alkaline solutions ($\ce{Na2CO3}$) with crude oil containing carboxylic acids to create micro-emulsions. The carboxylic acids react with the alkaline moieties to create an in-situ ...
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127 views

How to purify volatile haloalkanes prepared by Darzens halogenation?

We know that the Darzens method of substitution works on $S_n i$ and is considered the best method in terms of yield of product. Also the side products are $\ce{SO_2}$ and $\ce{HCl}$ so the ...
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757 views

Period of Vibrational Modes

I am trying to understand more about the period of vibrational nodes. Currently, I am interested in the wavelength of the $\ce{Si-O}$ bond stretch in silica. I think this value is roughly $1000\mathrm{...
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14 views

Synthesis of AgI/rgo

Synthesis of AgI/reduced graphine oxide using 80 mg of AgI and 1.25 wt % of RGO. This means we are adding 100mg of RGO(solute) to 80mg of AgI right?
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1answer
48 views

Why electrons move to Cu in galvanic cells?

I'm student who learning about chemistry, and I got problem about understanding why electorns move to Cu in galvanic cells. Let's think the reason for electrons going to Cu is that the standard ...
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1answer
60 views

Polyprotic Acid Titrations

Titrating a mixture of strong and weak acids will yield endpoints such that the volume of base required to reach each endpoint will be different for each acid, e.g. in a mixture of HCl and CH3COOH, ...
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1answer
56 views

How to determine if pressure surpasses capacity with the van der Waals equation of state?

I have to decide whether a $\pu{20 L}$ container with $\pu{0.8 kg}$ ethane can withstand the pressure at $\pu{373.15 K}$. The following information is given: \begin{align} b &= \pu{6.448x10^-2 ...
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1answer
282 views

Dependence of Van der Waal's constants with distance

Shouldn't the constant change as the intermolecular forces vary at different distances? Or is it the case that the constants have nothing to do with the forces because we are using the 4 gas laws i.e ...
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2answers
319 views

What is the exact relationship between the Pi conjugated bonds in organic molecules and fluoroscence of those molecules?

Some compounds are more fluorescent than others, and some of those are Rhodamine, Phenolphtalin, naphthalene, anthracene etc. I want to know why these exact molecules undergo such phenomena, what is ...
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1answer
993 views

How does electrolytic conduction depends on the size of ions & their solvation?

The textbook says, The smaller the effective size of the ion after solvation, the greater will be its conducting power." But, on the Internet, it is explained as follows: Radius decreases, ...
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1answer
4k views

Graph between PV & P, Boyle's Law and its interpretation

My text book says: At higher constant temperature, the volume increase and value of product PV should increase due to increase of volume at same pressure, but PV remains constant at this new ...
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1answer
272 views

Why must NaOH be in excess if we wish to measure the effect acid strength has on the enthalpy of neutralisation?

A few different acids are given i.e $\ce{HCl}$ , ethanoic acid, $\ce{H2SO4}$, ethanedioic acid. We want to conduct an experiment in which we measure the temperature rise for neutralisation as a ...
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1answer
919 views

Calculating Boiling Point of solution

I wish to calculate the boiling point of the following solution. (w/w) 78.8% Glycerol, 11.6% Propylene Glycol, 8.3% Water, 1.2% Nicotine (molar fraction) 0.5790 Glycerol, 0.1037 Propylene Glycol, ...
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1answer
82 views

If an atom of any element gained energy, does it always mean that its electrons gain energy too?

My book says ; "The transitioning of electrons in atoms from one energy level to another is associated with changes in the energy of the atom." But it hasn't made it clear whether or not the gaining ...
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1answer
146 views

Calculating cell-potentials

I have measured the cell potential between a number of metals e.g. Ni, Pb, Al, Cu and Zn by constructing a galvanic cell and then used a voltmeter to measure the potential. Now, if I want to ...
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2answers
559 views

Ordering compounds by boiling points

Here is a MC question from my chemistry professor: What is the correct order of boiling points for molecules: $\ce{CO2}$, $\ce{LiOH}$, $\ce{CH3OH}$, $\ce{CH2O}$? I am mainly confused about ...