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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Symmetry and Group theory [closed]

Could you tell me the symmetry classification of the vibrational modes of benzene? State which of them are IR active and which are Raman active from your calculations. Qualitatively sketch the ...
Shivam kumar's user avatar
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What is the exact definition of isotonic solutions?

Background of the Question I am a high school student so maybe my understanding of this topic is quite less, so apologies in case I have asked an elementary question. My chemistry sir taught that :- ...
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Why Henry's Law for solubility of gas is defined in two ways?

My school book (NCERT) states Henry's Law as: The solubility of a gas in a liquid is directly proportional to the partial pressure of the gas present above the surface of liquid or solution. and then ...
Divyansh Singh's user avatar
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Why is the entropy change of surroundings in free expansion zero?

I have read that what differentiates an irreversible process like adiabatic free expansion from its counterpart reversible process — isothermal expansion, which takes the system to the same final ...
Jeff Jefferson 's user avatar
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How did early chemists work out the number of protons in the nucleus?

I was reading about the history of the periodic table and the description of an element’s atomic number as its proton number. I couldn’t find the source again but it was stated that they figured out ...
powerful_bob's user avatar
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Cp and temperature range

The problems is: A substance melts at $\pu{300 K}$. At this temperature $\Delta_\mathrm{fus}H^\circ = 12 \pu{kJ mol-1}$. The heat capacities of the solid and the liquid are: $C_p(\text{solid}) = \pu{...
mary wøods's user avatar
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What exactly is the area used in the equation R=ρl/A to find the resistance of an electrolyte?

My textbook says the resistance $R$ of a water column filled with some electrolyte is $$R=ρl/A,$$ where $ρ$ is the resistivity, $l$ is the distance between the electrodes, and $A$ is the area of cross ...
Shivang Thakur's user avatar
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2 answers
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Use of Equivalent in organic chemistry

The question is taken from an engineering entrance exam in India(JEE 2024) If 3 mole of aniline is reacted with one equivalent of benzene diazonium chloride the maximum amount of aniline yellow formed ...
Rishikesh's user avatar
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How can a Michaelis–Menten formalism be used when enzyme concentration isn't constant?

I understand that $V_\mathrm{max} = k_3[\ce{E}]_0$ in ordinary Michaelis–Menten (MM) kinetics. According to the lecture notes provided by my university (I don't believe they are available online), ...
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Does pressure of vapor state affect vapour pressure of its liquid phase when both are in equilibrium in closed container? [closed]

In a closed container there exist a equilibrium between pure liquid and gaseous mixture i.e (gaseous mixture is ideal gas and liquid follows all classical chemistry laws). Also vapour state is ...
MultiUniverseExplorer's user avatar
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Solubility or reactivity of tantalum carbide and potassium polyselenides?

It is probably an unexplored system, but is there anything known about the low temperature thermodynamic equilibrium state of this? By 'tantalum carbide', I mean $\ce{TaC}$, and by potassium ...
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Derivation of form of rate laws [closed]

for a given reaction $A \rightarrow B+C$, I read in my book that the rate law has to be of the form $$ \frac{d[A]}{dt} = - k[A]^m $$ Can someone tell me (or point to some sources) on how we know the ...
Kryptic Coconut's user avatar
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Why is the boiling point of alcohols primary > secondary > tertiary? [duplicate]

If I have 1-butanol, 2-butanol, and 2-methyl-2-propanol, the boiling points of each are 117, 99, and 82 degrees Celsius, respectively. Why does that happen knowing that all of them have the same ...
omar waled's user avatar
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Activation energy [duplicate]

Can a reaction have zero activation energy? This was an assertion reason question in an entrance examination and different teachers had different answers. Please say weather this statement is true or ...
Tryon Doge's user avatar
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Filtering out sugars from liquid dye solution best scalable solution [closed]

I extract dyes from organic produce ideally we just want the colour-causing pigment in the final product. I have been extracting with ethanol as sugar is meant to be less soluble in it. I then add a ...
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Wave function in Schrodinger's model

I am trying to wrap my head around the Schrodinger's quantum mechanical model of an atom. According to the NCERT$^1$, the Schrodinger's equation is given by: $$\hat{H}\Psi=E\Psi$$ where $\hat{H}$ is ...
Chem-geek0's user avatar
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Understanding the relationship between Delta G and Kp, Kx and Kc

**Upon reading the chapter about equilibrium from my physical chemistry book, I was convinced that ΔG=−RTln(Kp)(1) and that Kp=Kx(P∑v)(2) where Kp is the equilibrium constant with respect to pressure ...
Kintoke 's user avatar
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Unknown oily substance forming during reaction of concentrated vinegar and calcium carbonate

I was attempting to produce calcium acetate by mixing concentrated vinegar (bought online) and calcium carbonate (sourced from wood ash) and ran a small scale test in a beaker before I reacted the ...
Metal Master's user avatar
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equation of state for a liquid in small ranges of temperature and pressure

consider the following question from Physical chemistry by Robert J. Silbey Robert A. Alberty Moungi G. Bawendi the answer is given to be $$V=Ke^{\alpha T}e^{-kp}$$ But I do not understand how this ...
Aarush Saharan's user avatar
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What is change in gibbs free energy of a reaction actually telling us? [closed]

$\Delta G=\Delta G^o+RT\ln Q?$ In this equation, what does $\Delta G$ mean? Is $\Delta G$ the change in gibbs free energy if we complete the reaction (convert all products to reactants)? That doesn't ...
ThatApollo777's user avatar
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Why atomic isotopes cause a different melting/boiling point? [duplicate]

Different experiments show that replacing atoms with isotopes can change intermolecular forces. For example, heavy water has a higher melting point than normal water, and D2 has a higher boiling point ...
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Trends in pKb for both acetic acid and water

I am trying to rationalise a result that I have recently measured in the lab. I'm measuring the pKb of different compounds in anhydrous acetic acid, using the procedure outlined in this paper (https://...
Stephen's user avatar
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Variable in Thermodynamics

While studying Physical Chemistry, I came up with this question. As I derive equation C_p-C_v, I found the equation (dQ/dT)p = T(dS/dT)p (d-> round) As I know, dQ=TdS so dQ/dT=(Tds/dT). and I'm ...
junstar's user avatar
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Different definitions for work in physics and thermodynamics [duplicate]

In physics, work is defined as the force applied on an object multiplied by the distance traveled by that object. However, in thermodynamics, work is defined as a function of the opposing force. For ...
SerMig1111's user avatar
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Henry's Law vs Raoult's Law Standard States for Activities

I am currently reading McQuarrie and Simon's Physical Chemistry and don't fully understand their discussion of standard states for activities. On page 990 they write (with a few minor adjustments to ...
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Splitting of electronic states in Tanabe-Sugano-diagrams

In Tanabe-Sugano-diagrams, different electronic transitions of term symbols of a given symmetry are shown. However, these electronic states arise due to splitting of term symbols of spherical to ...
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Pressure in Clapeyron and clausius Clapeyron equation

The Clapeyron equation is $\frac{\mathrm{d}p}{\mathrm{d}T}=\frac{\Delta S}{\Delta V}$. Here, is the change in pressure 'dp' actually a change in external pressure that is being applied on the whole ...
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Interpretation of a Phase Diagram

I am a bit confused about the correct way to interpret a phase diagram. I was told that the line separating the liquid and gas phases gives the vapor pressure of the liquid substance as a function of ...
Johnny Smith's user avatar
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Question Involving Bonding (VSEPR AND VBT)

So basically any chemistry book will tell you about the extent of overlapping in different orbitals. For formation of sigma bonds, head on overlapping happens. Chemistry textbooks always state that $p-...
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Does the electric field of a battery exist before a wire is connected outside?

Imagine a galavanic cell. What I am wondering is, what causes the inital oxidation of the less nobel metal to occur initally. Is the electric field there before you connect a wire, which would allow ...
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Why does enthalpy change and not internal energy help in determination of spontaneity?

Spontaneity of a process is measured by Gibbs Free Energy $$\Delta G= \Delta H-T\Delta S$$ $$\Delta H=\Delta U+\Delta (PV)$$ Is there an intuitive explanation for why Gibb's energy depends upon ...
Portuguese Man Of War's user avatar
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What is the pressure of triple point and melting point for ethyl chloride?

I need the information for pressure of triple point and melting point for ethyl chloride but on the internet I found only information for temperatures which are 134,5K and 134,82K.
Patricia's user avatar
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The use of H mass in mass defect and nuclear binding energy computations

I've noted that introductory general chemistry texts compute the mass defect (or mass difference) for radioisotopes using the proton mass $m_\ce{H}=m_{\text{p}}\approx1.00783 \ \text{u} $, instead of $...
Alexander's user avatar
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1 answer
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Lustre as a Chemical Property

In a text that I was reading, I found this paragraph on chemical properties: Chemical properties describe the ability of a substance to form new substances, either by reaction with other substances ...
user1297551's user avatar
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Doubt in Zeeman effect for sodium spectrum

I am reading an atomic molecular physics book (for Indian universities). You may not familiar with it. But you can download it from the link if you wish. So in the book it is mentioned that for normal ...
Sagar K. Biswal's user avatar
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3 answers
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How is it even possible that vapour pressure of liquid and vapour of solid are equal at freezing point? [duplicate]

My text book states The freezing point is defined as "the temperature at which the vapor pressure of the substance in its liquid phase is equal to its vapor pressure in the solid phase" Also ...
Aditya's user avatar
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1 answer
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Hydrolysis of $A_3B$ type weak acid-weak base salt

I know the formulae for weak acid-weak base salt of AB type. A peculiar question made me ask this. Do the formula for derived for AB type also hold for A3B type sal. For example: This is the question, ...
Aurelius's user avatar
1 vote
1 answer
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Does ionisation change the physical/chemical properties of an atom?

From what I have learned, the number of electrons on the outermost shell (called the valence electrons), determines the chemical properties of an atom, this is why elements in the same group have ...
user144179's user avatar
2 votes
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Can you tell if a HOMO to LUMO transition is allowed just by picturing the MOs?

Someone told me that they said the HOMO to LUMO transition is allowed in benzene and naphthalene just by looking at the MOs and without using the irreps for each orbital and the character tables? How ...
Audrix's user avatar
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Phase Diagram Vertical Lines

We had to create a phase diagram of H2O and NaCl. My professor mentioned that the vertical line I’ve encircled is at the weight % of 61.9. I was just wondering if this is proven through experiment or ...
chemstudent's user avatar
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1 answer
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I have fabricated a starch film impregnated with calcium carbonate, and the film is showing hydrophobic behaviour after addition of calcium carbonate

I have fabricated an extruded starch film, impregnated with calcium carbonate. After addition of calcium carbonate the contact angle of the film has risen suggesting a more hydrophobic surface. I have ...
Kshitij Madhu's user avatar
2 votes
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UV-Vis spectrum of 1,3-butadiene

Today I had the first lesson about UV-Vis spectrum. From the picture, the transition from HOMO to LUMOs of 1,3-butadiene depends on whether the structure is s-trans or s-cis. My question is: Why the ...
Shira's user avatar
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Why is reaction rate proportional to the order of reactants? [duplicate]

I know that for some elementary reaction $m\text{A}+n\text{B}\rightarrow\text{C}$, the rate of reaction is given by $-\frac{\text{dA}}{\text{dt}}=k[\text{A}]^m[\text{B}]^n$. Now if we consider the ...
Chitraksh Pandey's user avatar
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1 answer
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Doubt regarding Gibbs energy and Electrode potential

I have a doubt regarding the relation between Gibbs energy change and E cell, especially when calculating for redox reactions. This is a question I have seen on a website called "ExamSide ...
BK01's user avatar
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How to measure heat transfer and heat dissipation in a kitchen?

I am a chemistry beginner just starting to coming to grips with stoves and Bunsen burners. I would like to know, what kind of instrument can I use to measure the amount of heat transferred from a ...
Joselin Jocklingson's user avatar
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2 answers
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Is it possible to make thermite that detonates? [closed]

Why does thermite burn pretty slowly? Can it burn much faster if the components were ground to much smaller grain sizes? Can it be made to actually detonate--that is, the entire pile turning into ...
John Smith's user avatar
1 vote
1 answer
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What is the significance of PV in Enthalpy (H=U+PV)? Are we adding work twice in the equation? [duplicate]

I have 3 questions: Enthalpy is defined as: H = U + PV What exactly does PV signify? Also from the First Law of Thermodynamics ∆U = q + w w here means work (done by, say, the system). So, ∆H = q + w ...
apm's user avatar
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2 answers
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Photochemistry/Physicalchemistry - Fluorescence & Solvent Form

The hint from my instructor for the answer is related to Jablonski Diagram. The scenario: using fluorometer to measure fluorescence of a compound. How would my fluorescence results differ when ...
Syrianmousediggingsand's user avatar
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Heat capacity of calorimeter

The problem is: $\pu{30 mL}$ of water at $\pu{24.00 °C}$ were stored in a calorimeter in a laboratory experiment. Then, $\pu{40 mL}$ of water at $\pu{55.00 °C}$ were added to the calorimeter ...
Sherry Zakhari's user avatar
1 vote
0 answers
176 views

Who is more polar: acetonitrile or methanol?

According to data dipole moment of acetonitrile is around 4 while that of methanol is 1.7 but is said that acetonitrile is more soluble in non polar solvent that methanol. But shouldn't methanol be ...
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