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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Enthalpy change in an isothermal process at constant pressure [closed]

While studying thermodynamics I encountered a statement stating that " The Enthalpy change in an isothermal process is zero".I started analysing and got stuck when I came to the condition ...
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1answer
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Why do we use external pressure to calculate work done by a gas in case of compression instead of using internal pressure?

According to formula work done is (Resisting pressure X dV)? Then in case of compression, isn't the resisting force is internal Pressure? Then why we the formula for compression is same as expansion ...
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1answer
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Relation between standard silver-silver chloride electrode potential and solubility product of silver chloride

I learned that $\ce{E^\circ_{Cl^-|Ag,AgCl}, E^\circ_{Ag^+|Ag}}$ and $\ce{K_{sp}}$ of $\ce{AgCl}$ are related as $$\boxed{\ce{E^\circ_{Cl^-|Ag,AgCl} = E^\circ_{Ag^+|Ag} + \dfrac{\ce{RT}}{\ce{F}}\ln K_{...
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Why are protons more common than hydride ion?

I'm a high school student. I noticed $\ce{H+}$ ion is commonly present in my books while I didn't find any presence of $\ce{H-}$ ions in my books. However, I found on internet that $\ce{H-}$ also ...
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Does a change in Equilibrium position of a reaction affect the reaction rates of the forward and backward reactions?

In a reaction that is in an equilibrium state, when we change the pressure or concentration the equilibrium point changes. But does it affect the reaction rates of the forward and backward reactions?
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Why does magnesium have a greater ionization energy than lithium?

I'm a high school student and I'm learning about ionization energy and atomic radius of elements. I want to compare the ionization energy of lithium and magnesium. Here is the information provided in ...
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charge density of sea water in an electric field

How to find out the charge density of a block of sea water? If two electrodes were on the left and right wall of a small "tunnel" that is completely submerged in sea water or salt water with ...
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Predicting possibility of oxidation by observing Standard oxidation potential

How can we judge possibility of oxidation by seeing the oxidation potential? OR What is the relation between Standard oxidation potential (S.O.P.) and quality of oxidation ? By quality I mean the ...
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A liquid which climbs out of its pot [closed]

My Russian born wife recently asked me to buy her a skin remedy widely used in Russia. In English this is the oil of a plant called Sea Buckthorn. It is a thin yellow liquid. My wife put some of this ...
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Specific heat capacity of alcohol [closed]

A piece of iron of mass 0.27kg is immersed in a boiling water and and dropped into 0.10kg alcohol at 27°C. If the final mixture is 50°C, what is the specific heat capacity of the alcohol? (Specific ...
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1answer
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Is this true for conductivity of mixture of two solutions equal to the sum of conductivities of each solution?

Suppose $\ce{Na2SO4}$ has a conductivity $\pu{2.6 \times 10^{-4} S cm-1}$ and on mixing $\ce{CaSO4}$ to saturation, the conductivity becomes $\pu{7.0 \times 10^{-4} S cm-1}$. So, Is the conductivity ...
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How to do a capacitively coupled electrode?

I have an AUTOLAB potentiostat: working electrode (WE, Pt wire), counter electrode (CE, Pt wire), reference electrode (RE, Ag/AgCl solid state). I would like to capacitively couple the potentiostat ...
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What is the explicit difference between ICT and PET for sensors?

I've been reading about boronic acid based sensors for saccharides (glucose, fructose, etc). Boronic acids are able to complex with diols to form boronate esters and if there is a luminophore on the ...
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1answer
66 views

Can suspended solid particulate particles adsorb on surface?

Gaseous and liquid particles adsorb on solid surfaces. Can solid particles suspended in a fluid medium also adsorb on these surfaces in the same manner?
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Fields of Study in Chemistry [closed]

Is there a standard classification scheme for different areas of study and research for chemistry like mathematics has Mathematics Classification Scheme (MSC)?
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Does the vapor pressure of a substance depend on the presence of other gases?

The Clausius-Clapeyron equation (CC equation) can be used to find the (saturated) vapor pressure of a substance ie. the gas pressure at which the two phases (vapor + liquid or vapor + solid) reach ...
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Can a complex reaction have more than one rate determining steps?

I was solving some questions related chemical kinetics and encountered one question with multiple correct answer , the question is : For a complex (multistep) reaction, (a) the overall rate of ...
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1answer
38 views

What's the equilibrium pressure of CO2 gas over sodium hydroxide?

Many (too many) decades ago in physical chemistry lessons, I seem to recall that given the enthalpy changes of reactions, and maybe phase diagrams, one could work out what equilibrium a reaction would ...
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How practically to determine dispersion's Hamaker constant using CCC?

I know that Hamaker constants can be determined from CCC data. $$ccc=\frac{9.85 \cdot 10^4 \epsilon^3 k_B^5 T^5 \gamma^4}{N_A e^6 A^2 Z^6}$$ Where, $\epsilon$ is solvent dielectric constant, $N_A$ is ...
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Are pseudo-zeroth order reactions possible?

Are pseudo zeroth-order reactions possible? I have been taught that pseudo first-order reactions take place and they can be considered pseudo zeroth-order reactions because one reactant is in excess ...
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2answers
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Is strength of pi bonds greater than sigma bond of nitrogen molecule?

I am referring to molecular orbital (MO) theory. In the nitrogen molecule (and elements of lower atomic number) $\textrm{sp}$ mixing occurs and the sigma orbital set is raised above the pi orbital set....
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Hessian matrix and mass-weighted Hessian eigenvalues

If I have the Hessian matrix and the mass-weighted Hessian matrix for a system, I can find the normal modes from the mass-weighted Hessian and the force constants from the Hessian. I have a list of ...
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1answer
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Finding solubility of salts of polyprotic acids

Problem Given, for $\ce{H3PO4}$, $\mathrm{pK_\mathrm{a_1}=2.2}$ $\mathrm{pK_\mathrm{a_2}=7.2}$ $\mathrm{pK_\mathrm{a_3}=12.4}$ For the salt $\ce{Mg(NH4)PO4}$, $\mathrm{pK_\mathrm{sp}=12.6}$ and the ...
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Calculating electrons emitted when quantum yield is given

In a problem, the wavelength $\lambda$ of a monochromatic light, power $P$ of the source, and work function $\phi$ of the metal on which the light is shown is given. Quantum yield is $n$. I have to ...
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Intuition for relation between electrode potential and reaction quotient

Consider the following reaction in a galvanic cell: $$\ce{X(s) + Y+(aq) -> Y(s) + X+(aq)}$$ According to the Nernst equation, $$E =E_\circ - \dfrac{RT}{F}\ln\left(\dfrac{\ce{[X+]}} {\ce{[Y+] }} \...
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Why is “activity” of gaseous component equal to its partial pressure but that of aqueous component its concentration?

While solving an electrochemistry problem I had to calculate the reaction quotient of this reaction: $$\ce{2Fe(s) + 4H+(aq) + O2(g) -> 2Fe^{2+} (aq) + 2H2O (l)}$$ It turns out to be: $$\ce{Q=\dfrac{...
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1answer
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Is there any relation between reaction quotient and rate constant in the context of order of the reaction?

How many times will the rate of the reaction $$\ce{2 A + B -> A2B}$$ change if the concentration of substance $\ce{A}$ is doubled and that of substance $\ce{B}$ is halved? The given solution takes ...
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45 views

Ionic mobilities and conductivities of lithium and potassium cations in acetonitrile–propylene carbonate solution

Recently I calculated the ionic mobility and molar ionic conductivity values for $\ce{Li+}$ and $\ce{K+}$ cations in an acetonitrile–propylene carbonate binary mix solution (8:2 molar fraction ratio). ...
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What is the enthalpy of formation of benzene? [closed]

I was trying solve this question from my book: The combustion of one mole of benzene takes place at $298 \mathrm{~K}$ and 1 atm. After combustion, $\mathrm{CO}_{2}(\mathrm{~g})$ and $\mathrm{H}_{2} \...
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Can a battery be built where several electrodes share the same electrolyte?

If you have two metals i.e. iron / copper and an electrolyte solution you can make a battery. Typically all of the designs have several of these connected in series to boost the output. But I have ...
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Why aren't electrons included in the equilibrium constant expression?

This might be elementary, but why aren't electrons included in the equilibrium constant for a half-reaction? For example, for $$\ce{O2 (g) + 4H+ (aq) + 4e- -> 2H2O(l)}$$ we have $$Q = \frac{(a_\ce{...
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What is the Density of States and Fermi level for an isolated molecule?

I have difficulties understanding the Fermi Level and Density of states. The density of states ρ(E) at energy E is defined such that the number of states between energies E and E+dE is given by ρ(E)dE....
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Can't fit an exponential curve to the decomposition of hydrogen peroxide

I have carried out an experiment on the $\ce{MnO2}$ catalyzed decomposition of hydrogen peroxide. I would have expected the reduction in concentration to be exponential but when I fit an exponential ...
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1answer
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how to show the coordinate bond in avogadro?

I have this structure figure 1, I want to visualize by Avogadro, but the shape is not as I want like in figure 2 where I used Molden, so how can I make Avogadro draw the coordinate bonds.
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Linear algebra and Hess's law?

I am a high school student taking chemistry who was tasked to solve a large set of Hess's Law problems. Naturally I tried to find a way to get my computer to carry out this repetitive piece of work ...
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1answer
86 views

If something is not hydrophilic, is it necessarily hydrophobic?

Is it possible to create hydrophobic water? Two species are phobic within some medium under some conditions when they don't here together (cohere if they're the same species; adhere otherwise). To be ...
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1answer
75 views

Can we have an equilibrium constant for a reaction at constant volume?

Suppose we have a sealed container (fixed volume) and we introduce two gases $\ce{A}$ and $\ce{B}$. The two reactants $$\ce{A + B <=> C}$$ form another gas $\ce{C}$ with equilibrium constant $K$....
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Is there a parameter for degree of ‘mixedness’

So I was making coffee this morning and when mixing some milk into the black coffee, I wondered if there was some parameter or value in chemistry which describes how well mixed two liquids (or gases) ...
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Is it possible to create hydrophobic water?

I recently saw "hydrophobic water" in my school science fair. I have no idea on the procedure of how to make it, so, can I make it? I did google it and read some articles (zero helpful) and ...
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Why only active mass of a rectant reacts in a reaction? [duplicate]

The question is about active mass.My text book says active mass of the reactant takes part in a reaction not the whole mass.I cannot understand why this is so? Edit:please explain it in a lucid way as ...
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1answer
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What does water saturated oxygen mean? [closed]

What does water saturated oxygen mean in this question: The vapour pressure of water at 80º C is 355 torr. A 100 ml vessel contained water saturated oxygen at 80º C, the total gas pressure being 760 ...
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1answer
62 views

Why does adding excess NaOH prove amphoteric nature?

When 3+ hexaaqua ions react with hydroxide ions, the following set of reactions occurs: When we get to stage 3, a neutral ion has formed, and a white precipitate is created. Now, we know that for ...
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2answers
35 views

What is the cathode in NiMH batteries

What is the cathode in $\ce{NiMH}$ batteries? I’m not sure if it is $\ce{Ni(OH)2}$ or $\ce{NiOOH}$. I’m confused because I thought that these batteries are like $\ce{NiCd}$ batteries except better (...
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Units conversion of Henry coefficient in adsorption on solids [closed]

In a database of solid microporous materials I have the Henry coefficient in units of $\pu{mol kg^{-1} Pa^{-1}}.$ How to convert to $\pu{Pa^{-1}}?$ I tried to multiply by the molar mass of the sorbate ...
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1answer
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Are sudden adiabatic expansions reversible or irreversible? (Tyre burst problems)

Encountered Question: The tube of the tyre of a car is filled with air at $\pu{27^\circ C}$ and $\pu{2 atm}$ pressure. If the tube suddenly bursts, the final temperature of the air will be ($γ_\...
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How is the molar weight of C-12 equal to 12 gram ? Why is “g” not considered while calculating molar weight? [closed]

So, I was just pretty confused about how we simply multiply the "mass" of total nucleons in Carbon by the Avogadro Constant, to get the molar "weight" as 12 grams, shouldn't it be ...
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Understanding equivalence point [closed]

I read this passage: “It is important to emphasize that, while a strong acid/strong base titration will have its equivalence point had a pH of seven, the equivalence point does not always occur at pH ...
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Can alkali-doped exohedral fullerene molecules show superconducivity?

Alkali doped fullerenes are one of the few organic materials that show superconductivity. However, when attaching a new molecular system to a fullerene doped with an alkali metal, will it still show ...
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1answer
91 views

Calculating pH of aqueous ammonium hydrogen sulfide solution

I was doing the following question yesterday: Calculate the pH of a $\pu{0.1 M}$ solution of $\ce{NH4HS}$, given $\mathrm{p}K_\mathrm{b}$ of $\ce{NH3}$ is $4.74$, and $\mathrm{p}K_\mathrm{a1}$ and $\...
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1answer
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Understanding the Osmotic Pressure formula

$$\Pi = iMRT$$ Can this be rewritten as $\Pi = ORT$ where $O =$ osmolarity? The only reason I ask is because my book doesn’t talk about the relationship between osmolarity and molarity, but I came ...

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