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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What is the official method used to determine the Density of a solvent (e.g: Hexane)? [closed]

A relevant method to to determine the Density of a solvent (e.g: Hexane).
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What is the minimum number of given sets of information required to complete an ICE chart for an equilibrium reaction?

I'm considering creating a program that automatically completes an ICE chart/table when the minimum given information is provided. The reason I'm posting my question here is because I need to know the ...
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van der Waals equation for real gases [closed]

At what kind of temperatures, pressures, and volumes must I ignore the van der Waals constants $a$ and $b$? Please explain in detail as I really find these stuff hard while I solve questions at JEE ...
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What does the formula for freezing point depression tell us?

So, I know that the freezing point will fall, but doesn't the salt water then freeze over a range of temps? What exactly does the formula $$\Delta T = i \cdot m \cdot K_f$$ give? Here $\Delta T$ is ...
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Calcium chloride hydrolysis

I was wondering about $ \ce{CaCl2} $ hydrolysis. The most primitive answer would have been: $ \ce{Ca(OH)2} $ does not dilute that great, therefore it is not strong enough to have the $ \ce{Ca^2+} $s ...
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What is the effect of impurities on ice? [duplicate]

So, I know that the salt dissolves in the thin film of water on the surface of the ice, thus resulting in freezing point depression... but how exactly do i quantify this? Is there any effect on ...
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Will group 2 chlorides dissolve in water in water or react to produce distinct products? How does this differ by the type of salt? [closed]

I thought it'd dissolve... but am i wrong? I added calcium chloride to water, and it was smoking, i was so confused. Can someone explain happened? I am doing an experiment where i dissolve salts in ...
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Is the difference in bond dissociation energy of two bonds equal to the difference of the zero point energies?

Say I have a C-H bond and a C-D bond. Is the absolute value of the difference in ZPE of two bonds a valid way to calculate the difference in BDE?
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My Misconception of Entropy

It was recently brought to my attention that my understanding of entropy is wonky at best. In my experience, entropy was introduced (superficially at best) during general chemistry/foundations of ...
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Effect of impurities on melting point

This is a 10th-grade question. The melting point of a substance decreases with increase in presence of impurities in it. The melting point of ice decreases from 0 °C to -22 °C on mixing salt in it ...
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What is conductivity? [closed]

Definition for conductivity Raference to refer about it Equations of conductivity
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Defintion of Solubility in Different cases

How do we define solubility (in moles per liter) in cases when concentration of cation is not equal to the concentration of anion? e.g. When we put AgCN in an acidic solution (Leading to formation of ...
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Why does activation energy depend on temperature? [duplicate]

To me it makes sense that the activation energy $E_\mathrm a$, as given by the Arrhenius equation, doesn't depend on the temperature as the needed energy (potential energy) to start a reaction has ...
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If you accumulate 100 identical spheres how many will end up on the surface?

So far I have asked this question in physics, engineering and math sections but have not gotten an answer in three years. If you have 100 identical spheres and group them into A sphere shape, how many ...
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Wavelength of X-rays

What will be the wavelength of an X-ray, if we apply a potential difference of, say $\pu{20 kV}$ across the ends of the X-ray tube? Alright, I started with the modified de-Broglie equation- $$\Lambda=\...
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Missed out on High school science, how to get up to speed [closed]

(Australian here) I didn't pay attention in science from year 7 to 10, and completely jettisoned all science related subjects in year 11 and 12 (specifically Biology, Chemistry, Physics). 10 years ...
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Need for enthalpy of vaporization in calculating bond dissociation enthalpy

In our chemical bonding class we were given the following problem: I am confused by how the question says that you need to consider the heat of vaporization/sublimation for HBr and HI. Bond ...
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In what solvents does ionic association occur?

When a ionic compound like $\ce{NaCl}$ dissolves, it doesn't always full dissociate due to ionic pairing. This is measured by the van 't Hoff factor. Now, this is what I'm looking at for my chem ...
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How to reduce the surface tension of molten metals?

I'd like to reduce the surface tension of molten metals to reduce air bubbles by casting them like in this video with plaster. Actually the goal is to be able to cast gold without bubbles, but I guess ...
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Finding Ka of a monoprotic weak acid from pH and concentration of added sodium salt

A solution of $\pu{0.36 M}$ of the sodium salt of a generic monoprotic weak acid $\ce{HA}$ has a $\mathrm{pH}$ value of $8.782.$ $K_\mathrm{a} = ?$ Why doesn't the following formula work in this ...
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A steel sample was analysed for nickel

A steel sample ($\pu{0.3500 g}$) was dissolved in nitric acid and the resulting solution made up to $\pu{500 ml}$. The absorbance of this solution measured by atomic absorption was found to be $0.410$....
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Proof for second-order perturbation term of energy

In perturbation theory, if \begin{align}{\hat {H}} &= {\hat {H}^{(0)}} + λ{\hat {H}^{(1)}} \tag{1}\\ {ψ} &= {ψ^{(0)}} + λ{ψ^{(1)}} +λ^2{ψ^{(2)}} + ... \tag{2}\\ {E} &= {E^{(0)}} + λ{E^{...
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Why does Vapor Pressure decrease on addition of solute? [duplicate]

Consider a vessel with a volatile liquid in it. Let's say it has a vapor pressure $P^0$ when it is pure. Now a non-volatile solute is added to it. Its vapor pressure decreases as $P^0\chi_{solvent}$. ...
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Does a diatomic gas have one or two vibrational degrees of freedom?

Many sources claim that the vibrational degrees of freedom for a diatomic gas is one, but there are also a few which claim it to be two. Which is correct, and why is there even any ambiguity to begin ...
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Calculating Compressibility factor from the Van der Waals' Gas equation

So this problem has been bugging me for a long time. According to Wikipedia the compressibility factor $Z$ is defined as the ratio of the volume occupied by a real gas divided by the volume occupied ...
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2answers
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Polar protic solvents with melting point between between 0 °C and 25 °C [closed]

Need a solvent for a freezing point depression experiment. Acetic acid is the only one I know of, but it is not ideal due to the low freezing point depression constant. Any suggestions?
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Why do some elements with high electronegativity exhibit metallic properties?

Metals typically have low electronegativity, which makes them form ions easily and prefer making metallic bonds to covalent. However, some of them seem to disprove that. Take, for example, gold, lead ...
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When is Raoult's Law valid for solid-liquid solution?

Raoult's Law for solid-liquid solution is stated as such in my books that it is applicable for all non-volatile solutes. However different solutes must have different attractive or repulsive forces ...
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Calculating the cell potential of a half cell from two half cell equations [duplicate]

I understand the premise of the question and how to solve it but I don't quite understand why I'm a factor of 2 out: Construct a potential diagram (at $\mathrm{pH} = 0$) for the reduction of aqueous $...
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What is heterogeneous catalysis in gas phase?

Give examples of heterogeneous catalysis (i) in gas phase and (ii) in liquid phase. Now, I came to know that heterogeneous catalysis involves different phases between the catalyst used and the ...
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Artificial Muscle | HASEL's Reaction

I was watching a TED-talk on artificial muscle, HASEL, where the inventor demos that an insulated oil in the presence of electric potential field gets displaced due to Maxwell stress inside oil. ...
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Why is magnesium sulfate acidic? Why are my calculations showing that it is basic?

Let's say I was dissolving $\pu{1 M}~\ce{MgSO4}$ into water and I wanted to find its $\mathrm{pH}$. I would go right to the reaction of the dissociation of $\ce{Mg(OH)2}$: $$\ce{Mg(OH)2 <=> Mg^2+...
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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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How do i experimentally determine the vapour pressure of a solution? [closed]

So i wanna dissolve different salts in water and measure the vapour pressure of the resulting solution. I am doing this to compare the freezing point depression of different cations, used with the ...
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1answer
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Why is change in internal energy not equal to zero during a phase transition? [closed]

Many books state that when there is no change in temperature $\Delta U$ is equal to zero. Why is this not applicable for phase transitions? I have had this question for a while now and have been ...
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Figuring out formula of a hydrocarbon from amount of products obtained and reactants used

One mole of a hydrocarbon is combusted. The products obtained are cooled down to STP and occupy a volume of $89.6\ \mathrm l$. Oxygen required for combustion was $145.6\ \mathrm l$ at STP. Find the ...
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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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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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How to use Clausius-Mossotti equation to determine the molecular structure of a compound? [closed]

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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Polarising power

I don't understand this statement written in my textbook about the polarising power of cations. "If two cations have the same size and charge, then the one with pseudo noble gas configuration ( with ...
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Effect of pressure on transition temperature

I was wondering if someone can explain why the answer to the following question is volume instead of the others. If pressure has no effect on the transition temperature between two crystalline forms ...
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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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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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How do I find the final temperature of a calorimeter using specific heat capacities?

What is the final temperature of water and iron if a $\pu{30 g}$ piece of iron at $\pu{144 °C}$ was dropped into a calorimeter with $\pu{40 g}$ of water at $\pu{20 °C}$? Specific heat of water is $\pu{...
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Is the following rate law possible for the given reaction?

A researcher is investigating the following overall reaction: $$\ce{2C + D -> E}$$ The researcher claims the rate law for the reaction is written as follows: $\text{Rate} = k[\ce{C}][\ce{D}]$. Is ...
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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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How many moles NH4Cl must be added to NH3 to create buffer with pH=9?

How many moles of $\ce{NH4Cl}$ must be added to $\pu{2.0 L}$ of $\pu{0.10 M}$ $\ce{NH3}$ to form a buffer with $\mathrm{pH}=9$? Assume the addition does not change the volume of the solution ...
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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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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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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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