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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Find change in pressure for a van der waal gas [closed]

You are given $\pu{1 mol}$ of a Van der Waal gas and you have the volume change from $\pu{10 l}$ to $\pu{9 l}$ and the temperature changed from $\pu{273.15K}$ to $\pu{274K}$. Find $\Delta P$.
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Balancing a reaction where dichromate ion reacts with ethanol to give Cr(III) and carbon dioxide

I have only started to learn balancing redox reactions, and a recent question has me confused. The question is : Balance in both acidic medium and basic medium: $$\ce{Cr2O7^2- + C2H5OH -> Cr^3+ + ...
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Why is vapor pressure constant at boiling point?

At non-boiling point, I understand that when you add heat, temperature increases and also the amount of gas increases, so by using $PV=nRT$ at constant volume, the increase in $n$ and $T$ would ...
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How to use Clausius-Mossotti equation to determine the molecular structure of a compound?

A question in my exam came as follows: Explain the Clausius-Mossotti equation. How is it used in establishing the molecular structure of a compound? I have studied the Clausius-Mossotti equation and ...
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1answer
44 views

Finding concentration of hydronium ions in water after adding hydrogen chloride gas [closed]

A sample of hydrogen chloride gas, $\ce{HCl}$, occupies $\pu{0.932 l}$ at a pressure $\pu{1.44 bar}$ and at a temperature of $\pu{50^\circ C}$. The sample is dissolved in $\pu{1 l}$ of water. What is ...
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1answer
63 views

Kinetics question regarding Rate Law

The acid catalysed hydrolysis of an compound $\ce{A}$ at $\pu{303K}$: $$\ce {A ->[$k$] B}$$ has a half-life of $\pu{100 min}$ when carried out in a buffer solution of $\mathrm{pH=5}$ and $\pu{10 ...
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1answer
39 views

What explains the case hardening color effect?

Year 11 chemistry student here. I'm curious about how the case hardening effect works on metals. I know that when the electrons gain an energy 'level' or lose an energy 'level' they emit light at ...
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1answer
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Calculating numbers of moles at equilibrium given the volume of mixture and initial concentration of reactants [closed]

The equilibrium between three substances, A, B and C Is shown below. $$\ce{A(g) + B(g) <=> C(g)}$$ Initially there were $\pu{0.1 mol}$ of A and $\pu{0.2 mol}$ of B in the reaction mixture. A and ...
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1answer
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Why is the first ionization enthalpy of molecular O2 less than atomic O?

A cousin of mine asked for my help to answer one of his homework questions. It stated- Explain why- The first ionization energy of molecular oxygen $\ce{O2}$ ($\pu{1175 kJ mol-1}$), is lesser than ...
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Finding volume of carbon dioxide produced in combustion of methanol [closed]

The reaction for the combustion of methanol ($\ce{CH3OH}$) is seen below. If $\pu{1.0 mol}$ of methanol is completely combusted, what volume of carbon dioxide is produced. Assume STP ($\pu{273.15 K}$, ...
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Effect of pressure on barium oxide crystal [closed]

$\ce{BaO}$ has a rock salt type structure.When subjected to high pressure, the ratio of the coordination number of $\ce{Ba^2+}$ ion to $\ce{O^2-}$ ion changes to. a) $4:8$ b) $8:4$ c) $8:8$ d) $4:4$
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What experimenting readings can I do to measure freezing point depression of salt water? [closed]

I cant measure the dip in freezing point directly.... the molal constant of water is too low. For my experiment, im dissolving diff salts of equal concens in water and i wanna see which is best for ...
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1answer
46 views

How to experimentally determine the chemical potential of salt water? [closed]

I have NaCl dissolved in water. How do I find the chem potential?
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1/8 instead of 1/12 of mass of carbon atom as relative atomic mass [closed]

If we consider that 1/8 in place of 1/12 mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will: (1) Decrease by 1.5 times (2) Increase by 1.5 times ...
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2answers
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Is is valid to compare reaction quotient to $K_p$ as well as $K_c$?

Can I use the reaction quotient compared to $K_p$ to answer the following question? The solid $\ce{XY}$ decomposes into gaseous $\ce{X}$ and $\ce{Y}$: $\ce{XY(s) <=> X(g) + Y(g)}$ with a $K_p = ...
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ionic equlibrium [closed]

question is related to ionic euilibrium please answer option Q as soon as possible
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Evaluation of an element of a basis function and its derivative using some chemistry package [migrated]

Given some element and one of the basic functions of one of the Gaussian basis sets, I'd like to be able to recover the maximum value any of the basis functions can take, as well as their maximum ...
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Calculate inert molar flow rates in absorption column

In an absorption column the absorption of $\ce{CO2}$ from air to water is being studied. The in-flow of water is $\pu{5 dm3/min}$, the in-flow of air is $\pu{4.5 dm3/min}$ and the $\ce{CO2}$ flow is $\...
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Deriving an expression for reaction time in terms of the total concentration

Consider the dimerization of protein $\ce{A}:$ $$\ce{2A <=> A2}$$ with forward rate constant $k_1$ and backwards rate constant $k_{-1}.$ Derive the following expression for the reaction time in ...
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Can single molecules of C and O2 react in isolation, and if so how will momentum be conserved?

I am trying to figure out how is it possible to reconcile the reality of exothermic reactions, which means that kinetic energy is transferred to (heats) the surrounding matter, with the principle of ...
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1answer
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Why does the energy level of a particle in a box decrease with length?

I want to know the intuition of why L is in the denominator of the equation for the energy of a particle in a box. This helps explain why resonance is stabilizing without using molecular orbitals. ...
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1answer
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Dimensional Analysis: Conversion of units from m/s^2 to mi/hr^2 [closed]

I was given a dimensional analysis problem that is stated like this: The acceleration due to gravity is $\pu{9.81 m/s2}$. What is the gravitational acceleration expressed in $\pu{mi/hr^2}$? The ...
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1answer
177 views

Textbook problem with molar mass of carbon dioxide

$\ce{K2CO3}$ and $\ce{HCl}$ react to produce $\ce{CO2}$. In an empty flask ( m = $\pu{85.431 g}$ ) we put in the produced gas and the mass of the flask is now $\pu{85.510 g}$. After that we fill the ...
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Mechanism of decomposition of alkali metal halides in flames

A student recently asked an interesting question What happens when KCl is introduced in the Bunsen flame?. This apparently simply question led me to an interesting debate. We all know that emission of ...
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Interpreting a thermodynamics equation using a picture

Given $$ \frac{\partial \Gamma}{\partial p}\Bigg|_{t} =\frac{\partial \Gamma}{\partial p}\Bigg|_{v}+\frac{\partial v}{\partial p}\Bigg|_{t}\frac{\partial \Gamma}{\partial v}\Bigg|_{p} \tag{1}$$ where \...
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Finding atomic weight using Bragg's law [closed]

Plane of elemental FCC crystal diffracts X–ray ($\lambda = \pu{0.154 nm}$) at Bragg angle $90º$. Density of crystal is $\pu{4 x 10^4 kgm-3}$. Atomic weight of elemental solid is: a) $22$ b) $44$ c) $...
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2answers
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Chemical potential and gibbs free energy

I would like to ask why the $\Delta_rG_1 = -RT\ln K + RT\ln Q$ is not equal to $Δ_rG_2$ numerically as shown in the figure where I derived $\Delta_rG_2 = RT\ln Q$ using a cyclic ring since $\Delta_rG$ ...
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2answers
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What does enthalpy of formation at room temperature mean?

$\ce{AlCl3}$ has a standard enthalpy of formation some high negative value at $298\ \mathrm K$ $(-705.63\ \mathrm{J/mol})$. It means it's an exothermic reaction i.e will release heat. But my question ...
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How is a photoelectron spectrum assigned?

The photoelectron spectrum of a given molecule is commonly used as experimental evidence of the energy ordering of molecular orbitals (See here: 10.4: Photoelectron Spectroscopy, and many other ...
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1answer
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What happens when the amount given doesn't allow for equilbrium to be achieved in a reaction?

The reaction $$\ce{A.3H2O(s) <=> A.H2O(s) + 2H2O (g)}$$ has a $K_p = \pu{400 mmHg2}$ One millimole each of $\ce{A.3H2O}$ and $\ce{A.H2O}$ are taken in a $\pu{1 liter}$ container at $\pu{300 K}$ ...
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What is the influence of citrate on PEG-modified polyacrylamide hydrogels?

I've been having a puzzle explaining the experimental results with the citrate anions and PEG modified polyacrylamide: According to the experimental data there is a hydrogel swelling whenever citrate ...
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Kinetics of Decomposition of Hydrogen Peroxide [duplicate]

Consider the decomposition of Hydrogen Peroxide: $$\ce{H2O2 -> H2O + 1/2O2}$$ The rate law for this reaction is : $$\text{Rate} = k[\ce{H2O2}]$$ Further $$\text{Rate} = -\frac{\mathrm d[\ce{H2O2}]}...
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Is there a way to theoretically estimate the overpotential losses in a battery?

Me and my team are currently designing a battery and are looking to do some pre-experimental analysis of different battery chemistries based on their overpotential losses. I am aware of the Butler ...
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Can Na2S + H2SO4 react to give Na2SO4 + H2O? [closed]

Can $\ce{Na2S + H2SO4}$ react to give $\ce{Na2SO4 + H2O}$ or $\ce{Na2O + H2O + SO2}$? In my textbook, it has been given that the product will be $\ce{NaOH + H2O + SO2}$. Can also the other two ...
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1answer
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Finding the Freundlich adsorption isotherm from the graph of log(x/m) v/s log(p)

The following problem was asked in JEE Mains 2020 (Sept 2, Shift 1), The mass of gas adsorbed, $x$, per unit mass of adsorbate, $m$, was measured at various pressures, $p$. A graph between $\log\frac ...
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Does anyone have experience with polycaprolactone?

I am trying to create an emulsion from polycaprolactone. My efforts thus far have resulted in unstable emulsions which sediment and coalesce after some time. This is what I have tried: Dissolve 5g of ...
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Cell potential for redox titration of iron(II) with cerium(IV)

Calculate $E_\mathrm{cell}$ for an electrochemical cell consisting of SCE and a platinum wire indicator electrode dipped in a titration vessel containing $\pu{25 ml}$ $(\pu{0.01 M})$ solution of $\ce{...
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How does current start to flow when galvanic cell is first connected?

Using the Daniell Cell as an example, where in the steady state we expect zinc to be oxidised and copper to be reduced spontaneously due to the overall reduction in Gibbs free energy, how does the ...
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The Curious Case of the equivalent weight

Please read the reference points given at the end. I understand the following about equivalent weight. Firstly it is given by, $Equivalent\:Weight= \frac{Molar\:Weight}{Valence\:Factor}$ And secondly, ...
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1answer
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Determine if stuff is Potassium Alum

How can one determine (at home) if the product shown below is Potassium Alum? I held a piece of it in a gas flame (assuming that the flame would become violet if potassium were present), but there was ...
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Effect of adding pure solid/liquid in heterogenous equilibrium

QUESTION Consider the following reaction as an example: $$\ce{NaNO3(s) <=> NaNO2(s) + 1/2O2(g)}$$ Once this reaction has achieved equilibrium and then if we added pure $\ce{NaNO3}$ to this ...
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Without attractive forces, why would there be only ideal gases? [closed]

I've read this statement in several places. What is the importance of attractive forces for solids and liquids?
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How to calculate membrane potentials?

I have recently been reading about membrane potentials in the cell and how they are derived. The textbook (Guyton and Hall Textbook of Medical Physiology, 13th Ed) gave this equation: $$EMF=\pm\frac{...
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How does work from other sources affect Gibbs free energy of the system?

In most physical chemistry textbooks, Gibbs free energy is given like this: $$\Delta_\mathrm rG = \Delta_\mathrm rG^\circ + RT\ln Q\tag{1}$$ and Gibbs free energy is part of this three-way ...
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1answer
35 views

Meaning of Partial Half-Life for Two Parallel Reactions

Consider two parallel reactions: $$\ce{A -> B }\tag1$$ and $$\ce{A -> C}\tag2$$ What is the meaning of partial half life of the equation $(1)$ and that of equation $(2)$ with respect to ...
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1answer
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Experiment to demonstrate Dalton's Law of Multiple Proportions

Is there an experiment that I can do in the lab with middle or high school students to demonstrate Dalton's Law of Multiple proportions ? For example, the reaction of $\ce{C}$ and $\ce{O2}$ to give $\...
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2answers
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Why is the units of rate constant dependent on the order of the reaction?

In many textbooks, it is written that For order (m + n), the rate constant, k has units of mol1−(m+n)·L(m+n)−1·s−1 However, by the Arrhenius equation, k can be expressed as k = PZexp(-Ea/RT) and ...
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Can carbon dioxide be reduced to carbon monoxide and oxygen to produce energy?

There are lots of questions about reducing or burning CO2 to carbon and oxygen to solve climate change, but of course that wouldn't work because it takes a lot of energy. But carbon monoxide is more ...
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What exactly happens during dipole induction (dipole induced dipole forces)- if anyone can explain just why this happens?

When a dipole is in vicinity of a polarisable molecule it induced a partial charge on the molecule by creating a dipole, is what I've been taught.I want to know whether the dipole formation of the ...
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why heavier transition metals can stabilise higher oxidations states [duplicate]

I believe similar questions have been asked but this is different and the answers I have looked at don't answer this question. I have read that oxidation states of heavier transition elements (Ru, Os ...

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