What is Physical chemistry: Definition and 150 Discussions

Physical chemistry is the study of macroscopic, and particulate phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mechanics, analytical dynamics and chemical equilibrium.
Physical chemistry, in contrast to chemical physics, is predominantly (but not always) a macroscopic or supra-molecular science, as the majority of the principles on which it was founded relate to the bulk rather than the molecular/atomic structure alone (for example, chemical equilibrium and colloids).
Some of the relationships that physical chemistry strives to resolve include the effects of:

Intermolecular forces that act upon the physical properties of materials (plasticity, tensile strength, surface tension in liquids).
Reaction kinetics on the rate of a reaction.
The identity of ions and the electrical conductivity of materials.
Surface science and electrochemistry of cell membranes.
Interaction of one body with another in terms of quantities of heat and work called thermodynamics.
Transfer of heat between a chemical system and its surroundings during change of phase or chemical reaction taking place called thermochemistry
Study of colligative properties of number of species present in solution.
Number of phases, number of components and degree of freedom (or variance) can be correlated with one another with help of phase rule.
Reactions of electrochemical cells.

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  1. Govind

    Gibbs free energy of activation and activation energy

    Let's consider a reaction A (reactant) -> B(product) and activated complex is denoted by C. This graph ( potential energy vs reaction coordinate ) tells us that reactant need some amount of activation energy (Ea) to convert in product, which has low potential energy which is shown here in...
  2. Dario56

    Concept of Absolute Thermodynamic Activity

    In the textbook Electrochemical Systems by Newman and Alyea, Chapter 14: The definition of some thermodynamic functions, chemical potential of component (ionic or neutral) is written as a function of absolute activity: $$\mu_i=RT\ln(\lambda_i)\tag1$$ where ##\lambda_i## is the absolute activity...
  3. tbn032

    B Exploring the Alpha Particle-Electron Interaction in Gold Foil Experiments

    My current understanding: The mass of alpha particle is approximately 7340.6 times higher than the mass of electron.in the gold foil scattering experiment the deflection of alpha particle due to electron is approximately zero. The reason that is given is that since the electron is much lighter...
  4. tbn032

    Question about the collisions of the molecules in an ideal gas

    (The equation of ideal gas is PV=NRT.if P=1atm,N=1mole,T=0°K,R=gas constant then volume = zero. Hence, the volume of an individual molecule of ideal gas is zero) An individual molecule of ideal gas is assumed to have zero volume. The molecules of ideal gas are assumed to be dimensionless points...
  5. tbn032

    Limits of Partial Charges in Dipoles

    In my book it is written "Ends of dipole possesses partial charges. Partial charges are always less than the unit electronic charge (1.6×10−19 C)". Suppose in a double bond(two electron is shared by each atom) or triple bond(three electrons are shared by each atom), can the electronegative atom...
  6. L

    Calculating the Radius of a Hot Air Balloon to Withstand a Load of 300 kg

    The result is supposed to be 12,2 m but every time I get 8,016 m... I used for example this formula >r=m/[(density of air-density of hot air)*(4/3)*pi] For density I used > rho=(p*M)/(R*T) Am I forgetting something? Thanks in advance.
  7. Dario56

    DLVO Theory of Colloid Stability

    DLVO theory gives the curve of potential energy vs distance of two colloid particles. Potential energy curve is derived for colloids being only electrostatically stabilized and not sterically. Looking at the image below which shows potential energy curve, we can see two local minima and one...
  8. Dario56

    What is the role of surface interactions in the stability of microemulsions?

    Unlike emulsions, microemulsions are thermodynamically stable. Its stability is often explained by entropy changes brought about by dispersing liquid in another liquid, however this can't be the whole story behind its stability since dispersing liquids also happens in regular emulsions and they...
  9. M

    Calculating the Density of Kr: A Guide

    Hello. Firstly, I've calculated the density of Kr ( = 3.74 g/dm3), and I know that the p (fluid) = ρ * h * g. And then I've used the following equation: p1*V1 = p2*V2, and therefore: p1*V1 = ρ * h * g * (m/ρ) => p1*V1 = h * g * m. (h = 3.0153 m) Is that correct? Please, how could I calculate...
  10. Dario56

    Maximum non - PV Work at Constant Temperature and Pressure and Reversi

    When we talk about systems at constant temperature and pressure, maximum amount of non-PV work can be extracted if process is carried reversibly and in that case it is equal to change in Gibbs energy of the system (decrease in Gibbs energy if system does non - PV work, A.K.A work is extracted...
  11. Dario56

    Entropy Changes in Electrolytic/Galvanic Cell?

    One of the most fundamental equations in chemical thermodynamics states: $$ \Delta_rH_m^⦵ = \Delta_rG_m^⦵ + T \Delta_rS_m^⦵ $$ If we look at this equation in context of net chemical reaction in electrolytic or galvanic cell, it is usually interpreted as follows: Enthalpy of reaction denotes...
  12. Jamister

    Quantum Where Can I Find Rigorous Books on Physical Chemistry for Master's Level Study?

    I'm master physics student looking for books in physical chemistry for stuff like born Oppenheimer Approximation and more. Most books give hand-waving proofs and I'm looking for a book which is more rigorous. Thanks
  13. J

    Standard enthelpies of formation of carbon nanotubes etc.

    I am curious about the standard enthalpies of formation of carbon nanotubes, diamond, carbon buckyballs, graphene, etc. I read from physics forums that the standard enthalpies of formation of these allotropes of carbon are small. However, since diamond is fabricated naturally under extreme...
  14. T

    Reciprocal lattice for FCC and diffraction peaks

    My issue is more with the steps to approach rather than the calculations. I was just wondering if someone could confirm my approach to be correct. As it asking for the reciprocal lattice of an FCC I assume this would mean I need to use the points on the BCC to calculate the geometrical...
  15. N

    Question about using the ICE table

    This is how I started my ICE table: $$CO(g)$$ $$H_2O(g)$$ $$H_2(g)$$ $$CO_2(g)$$ Initial (mol) 0.40 1.00 0 0 Change (mol) -0.40α -1.00α 1.4α 1.4α Equilibrium (mol) 0.40-0.40α 1.00-1.00α 1.4α 1.4α (or should I use 0.225) I am not sure if my table is correct. When I work out the total...
  16. Sophrosyne

    B How to think of molecular orbitals quantum mechanically

    The electrons in a molecule are said to be in a quantum superposition state in terms of their position/spin/momentum. But when you look at a molecule like water at a chemical level, it has a very specific shape corresponding to the P orbitals of the outer shell of the Oxygen atom. The two...
  17. Sophrosyne

    B Why is an electric arc needed for spectroscopy of clear gases?

    To obtain spectroscopy on a gas like hydrogen or helium, an electric arc is passed through a container of the material, and then the emitted light is viewed through a prism which breaks it up into its component wavelengths. There are sharp lines which are formed, caused by excitation of the...
  18. Aleoa

    Can I Start Studying Physical Chemistry Without a Chemistry Background?

    Hi guys, i'm a computer scientist with no background in Chemistry and I'm very interested in the field of Physical Chemistry. Do you think i can directly start to study a Physical Chemistry book ? If yes, do you have some books to suggest ?
  19. Wrichik Basu

    Chemistry Comparing Physical Chemistry Textbooks: Atkins vs. Levine

    I want some undergraduate level (or postgraduate level will also do) books on physical chemistry. I've got two books: one by Ira Levine and the other by Peter Atkins. But both these books contain only huge amounts of thermodynamics. Other topics are almost not touched upon. I want a book that...
  20. S

    Difference between chemical physics and physical chemistry

    What is the difference between physical chemistry and chemical physics?
  21. G

    Which physics for physical chemistry?

    Hey guys, I was wondering if algebra based physics will be useful or I will be in a disadvantage? I’m doing a minor in chemsitry and math. So I’m not sure when I will take PCHEM. Probably after partial differential equations I will take it. I’m hoping to take it in fall 2019 or spring 2020.im a...
  22. R

    Studying What Additional Resources Can Help With the Physical Chemistry ACS Exam?

    I am taking the second semester of physical chemsitry (quantum, spectroscopy, and some stat mech). I was wondering if there are any resources outside of the ACS study guide and open course ware. I'd really like some practice tests if possible so I can see what I need to study. Also, any lecture...
  23. B

    Physics of a chemical reaction: looking for textbook recs

    I'm currently doing a literature review on ultracold chemistry with an emphasis on collisional theory and quantum phenomena. I'm an undergraduate physics major, and I'd start my discussion of this topic by moving from basic Newtonian conservation laws and concepts like Coulomb repulsion to the...
  24. C

    Question Related To Volume Strength Of H2O2.

    1. Question Statement and details : 500 mL of 56V H2O2 is kept in an open container due to which some H2O2 is decomposed and evolves 8gm O2 simultaneously, during the process some H2O also vapourizes.Due to all these changes final volume is reduced by 20%. Find final volume strength of H2O2...
  25. L

    Please check my math about this engine efficiency calculation

    Hello. I wanted to see how much more efficient a car would be if hydrogen and oxygen (created through electrolysis of water) were injected into the engine alongside gasoline. I got lost when I found out that I would need 241.8 kJ/mol of water to electrolyze it...
  26. Sophrosyne

    B The Dirac equation and the spectrum of the hydrogen atom

    I was reading that one of the successes of the Dirac equation was that it was able to account for the fine structure of some of the differences in the spectrum of the hydrogen atom. But the Dirac equation is about subatomic particles moving at relativistic velocities. But an electron around the...
  27. B

    Equation of states for a gas that forms dimers

    Homework Statement Show that to a first approximation the equation of state of a gas that dimerizes to a small extent is given by, ##\dfrac{PV}{RT} = 1 - \dfrac{K_c}{V}## Where ##K_c## is equilibrium constant for ##A + A \iff A_2## Homework EquationsThe Attempt at a Solution Using virial...
  28. B

    Kinetics question (Chemical engineering)

    Hey! I have a question regarding this question that I have to answer. It is about the kinetics of a substance X whose product is 2Y. It is in Swedish and here is the translation: The absorbance of a 0,030M-solution of X was calculated with the help of a Spectrometer. The Spectrometer was...
  29. J

    Flux-flux correlation function under Feynman's path integral

    This is a chemically inspired problem, but the path is fully quantum mechanics and a bunch of integrals. How does one calculate fully quantum mechanical rate ($\kappa$) in the golden-rule approximation for two linear potential energy surfaces? Attempt: Miller (83) proposes...
  30. C

    Negative Free Energy - Physical Chemistry

    Homework Statement Hydrogen peroxide can be prepared in several ways. One method is the reaction between hydrogen and oxygen, another method is the reaction between water and oxygen. Given the ΔG°rxn values for each reaction, which method (reaction 1 or 2) requires less energy under standard...
  31. ReidMerrill

    Physical chemistry: Energy operator and eigenfunction

    Homework Statement The energy operator for a time-dependent system is iħ d/dt. A possible eigenfunction for the system is Ψ(x,y,z,t)=ψ(x,y,z)e-2πiEt/h Show that the probability density is independent of time Homework Equations ĤΨn(x) = EnΨn The Attempt at a Solution [/B] I understand the...
  32. B

    B Why are there only two colorful metals?

    I think there are only two metals, Copper and Gold , that exhibits some color other than silver or gray. I went to a science exhibition where samples of almost all metals where kept, I think I could only see Copper and Gold having different colors. Why is it so ? why not other metals show colors ?
  33. B

    I Why triatomic gases have internal energy 7RT/2 ?

    This table is given in my book, $$\begin{array}[c!c!c!c!] \text{ }&\text{ Transitional }&\text{ Rotational }& \text{ Vibrational} \\ \hline \text{Linear molecules} & 3&2& 3N -5\\ \hline \text{Non-Linear molecules} & 3&3& 3N -6\\ \hline \end{array}$$ It is also given...
  34. R

    Question about Organic Chemistry and Physical Chemistry

    Hi. I have a question about Organic and Physical Chemistry. I have already finished General Chemistry I and II and got decent scores on both of them (B on both of them). I am interested in taking Organic Chemistry, then Physical Chemistry afterwards. I know that both are different from General...
  35. T

    Estimating the final pressure of a transformation

    Homework Statement If the Helmholtz Free Energy remains constant, estimate the final pressure of 1.0mol of an ideal gas in the following transformation: (1.0atm, 300k) → (pfinal, 600k). Given Sgas = R. Homework Equations A = U - TS dA = -SdT - pdV The Attempt at a Solution If the Helmholtz...
  36. Thales Costa

    Change in Enthelpy for Nitrogen at constant temp

    Homework Statement Calculate ΔH for 2 mols of Nitrogen for the following transformation: 1 bar, 21°C → 200 bar, 21°C Given that molar Cp = 4R 2. The attempt at a solution How am I supposed to find the ΔH? From what I learned, there can only be a change in enthalpy when there's a change in...
  37. V

    A Question about Chemical Equilibrium

    say we have a reaction: N2O4 <====> 2NO2 for this reaction,if initial number of moles of N2O4 is 'a' can we write t = 0 a - at equilbrium a-x...
  38. V

    A problem in ionic equilbrium

    Homework Statement please see the attached image 1998 ,b part question [/B]Homework Equations none The Attempt at a Solution i thought that Agcl would give Ag+ and cl- ions whose concentration can be found from Ksp as √Ksp,this Ag+ reacts with NH3 to give Ag(NH3)2+ (reverse of the given...
  39. sara lopez

    Thermodynamics: air expansion in a cylinder

    Homework Statement Consider air expansion inside a cylinder. Assume that the volume and initial pressure is 1 ft^3 and 1500 PSI ABS respectively. If the expansion process is reversible and the path is given by P.V^1.4=constant. Calculate the total work done by the gas to reach the final volume...
  40. S

    Force constants of DCl and HCl

    The force (spring) constant of HCl 477.8 N/m, and the force constant of DCl is 487.95. Why should these values differ by 10 N/m? Is a D-Cl bond somehow stronger than an H-Cl bond?
  41. Nader AbdlGhani

    What Does an Equilibrium Constant Value of 1 Mean and When is it Expected?

    When does the value of the "Equilibrium Constant (K)" equal one ? and what does that mean ?
  42. Elena14

    Dalton's law for ideal gases at different temperatures

    How would Dalton's law be affected when there are two ideal gases in a container at different temperatures? Let the gas with higher temperature be gas A and the gas with lower temperature be gas B. Then heat will be transferred from gas A to gas B due to which kinetic energy of the molecules of...
  43. K

    Physical Chemistry Homework: Equilibrium Constant and Gas Properties

    Homework Statement I have the following task: A chemical reaction 2 A(g) <-> B(g) + C(g) has an equilibrium constant defined by: ln=0.8+ 1050/T−1,3.105/T² a) What is K at 400K? Calculate ΔrG0 In a volume of 5L you get 2 moles of A and 0.5 moles of B. Reaction still proceeds at 400K. Consider...
  44. B

    Contradiction of Gibbs adsoprtion?

    1. Surfactant molecule is made from water-loving head and grease-loving tail (Figure 1). http://tinypic.com/r/2j2gdah/9 (Figure 1) My question: How do we measure the cross-sectional area of the alkyl chain of surfactant? Do we measure it vertically (refer to GREEN DOUBLE ARROWS of Figure 1) or...
  45. V

    Physics or physical chemistry

    I'm currently in my first year of a MSc in physical chemistry and in the process of deciding what topic to choose for my thesis (most likely starting around april). I think my personal interests lie more on the side of physics than chemistry (I have only become sure of it this year). My...
  46. M

    Number of molecular hits from air onto a surface

    Homework Statement Compute the average number of molecular hits, per unit time, experienced by a square inch of surface exposed to air, under normal conditions. Assume air is a mixture composed of 80% N2, 20% O2, both of which are assumed to be ideal gases. You will have to perform angular...
  47. J

    Entropy of Liquid water Calculation.

    Homework Statement Calculate the ΔS° when 0.5 mole of liquid water at 0°C is mixed with 0.5 mole of liquid water at 100°C.Assume Cp=18cal/deg mole over the whole range of temperatures. Homework Equations ΔS=∫ Cp/T dT
  48. M

    Schools Question about Physical Chemistry Graduate School

    I'm currently a freshman a MIT. I was planning to do a Chemistry and Physics double major but after looking at the requirements for a Chemistry minor, it wouldn't take any additional classes to do a Physics and Math double major with a minor in Chemistry. The reason this is appealing to me is...
  49. MexChemE

    Exploring Thermo in Batman: Arkham Origins

    Hello, PF! Days ago, while playing Batman: Arkham Origins, I was wandering through the Batcave when I noticed something that caught my eye immediately. There's a nice, cozy lab in there which includes a blackboard where Bruce Wayne apparently did some kind of thermodynamic calculations, which...
  50. Ariel Jo

    Supercooled Steam Homework: Solving for Tf, Condensation Fraction & ΔS

    Homework Statement You have 0.50 mol of steam which has been supercooled to 95˚C at 1 atm. Since the steam is below the boiling/condensation point, it proceeds to partially condense into liquid water. This happens in a thermally-insulated vessel at constant pressure. (a) When the system...
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