Questions tagged [thermodynamics]

Applicable to questions about heat, energy, work, and their interconversion in chemistry. See the tag wiki for a detailed list of topics. Questions tagged may also be tagged with [enthalpy], [energy], [free-energy] where appropriate.

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Why does the equation for chemical potential apply to liquids and aqueous solutes?

The equation for chemical potential of a gas can be derived as such: At constant temperature, $$\mathrm dG = V\,\mathrm dP \label{eqn:1}\tag{1}$$ Substituting with the ideal gas law $PV = nRT$, $$\...
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Understanding the molar free energy to simulate phase separations (Na2O-SiO2)

I am a mathematician and I want to understand the molar free energy model given in Kim and Sanders (2020) Equation (1), that is, \begin{equation} f(c,T) = RT \big(c \log(c) + (1-c) \log(1-c)\big) + \...
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thermodynamic equilibrium

A thermodymic system is said to be in equilibrium if it satisfies the two conditions : 1-The system’s macroscopic properties remain constant with time. 2-removal of the system from contact with its ...
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2 votes
2 answers
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Mathematical models of Vaporization-Condensation dynamics

I am a mathematician now studying an introductory chemistry course. Consider a liquid in a closed container, at (say) room temperature. Then some of the liquid will vaporize. Then some of the ...
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Water Vapor content at equilibrium in vacuum [duplicate]

Given a hard bodied vacuum sealed container $C$. $C$ itself is internally divided into two sealed sub-containers $C_{lower}$ and $C_{upper}$ (each having volume $V$ $m^3$). $C_{lower}$ is completely ...
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why is the temperature on the y-axis

I am currently reading an article for class on molecular dynamic simulations used to calculate some thermodynamic properties of various isocyanates. One of the figures that pertains to the results ...
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How does the enthalpy change of bond enthalpy relate to enthalpy changes of formation? What's the difference? [duplicate]

The enthalpy change = sum of bond energies broken (reactants) - sum of bond energies made (products). Then I read The enthalpy change = sum of the enthalpy change of formation of products - sum of the ...
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Can general purpose compressors be used for a specific gas without modification?

Air compressors are commonly used for all sorts of purposes related to compressing air above 1 atm. My question is, could an air compressor be used for a specific gas without modification? For example,...
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Would laying an atom thick piezoelectric material near a heat source generate current? [closed]

From what I’ve read, a piezoelectric material (like quartz) generates current from squeezing the molecule lattice and deforming it to make the positively charged atoms on one side and the negatively ...
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1 vote
1 answer
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Finding relation between Gibb's free energy and equilibrium constant for a homogeneous gaseous phase reaction

I was trying to find relation between Gibb's free energy change and equilibrium constant for the following homogeneous gaseous phase reaction at constant temperature $$\ce{aA +bB }\rightleftharpoons \...
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Why is octasulfur present in equation for standard enthalpy of formation of sulfuric acid?

Write a balanced chemical equation corresponding to the standard enthalpy of formation of $\ce{H2SO4}.$ \eqref{rxn:r1} is the given answer, \eqref{rxn:r2} is my answer: \begin{align} \ce{1/8 S8 (s) + ...
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What do they mean with temperature in the formula for enthalpy?

I'm studying enthalpy and I'm having a real hard time trying to conceptualize it. I can do the exercises and know the formulas but I feel like I lack an understanding of what it actually is. One of my ...
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Misconception regarding mean ionic activity coefficient and applying it to equilibrium constants

I probably have some simple misconception about the mean ionic activity. The mean ionic activity coefficient is defined as $$ \gamma_{\pm} = \sqrt[^{p+q}]{\gamma^p_+\gamma^q_-} \tag{1} $$ I'm just not ...
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Reversible process at constant temperature and pressure

A reversible process is said to be a process in which the system is in equilibrium with its surroundings during the whole process( pressure and temperature equilibrium). When we derive the maximum ...
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Shielding vs electron-electron repulsion

Example of shielding: (source) The last electron in the 6s subshell of $\ce {Cs}$ is shielded from the nucleus by the inner electrons. Example of electron-electron repulsion: The electron affinity of ...
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2 answers
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Spontaneous reaction between chlorine and a hypothetical atom

Suppose, my hypothetical element is $\ce X$, whose first ionization energy is $\pu{200kJ/mol}$. An atom of this element will react with an atom of chlorine (assume that I've already dissociated a ...
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2 votes
1 answer
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My book's claim about the shielding effect of s,p,d and f electrons

It's a relatively unknown Bangladeshi book. It's called "Chemistry-First Paper (Class XI-XII)" by Professor Haradhan Nag According to my book, "Electrons of s and p orbitals produce ...
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Extent of Melting of Bonds or Intermolecular Forces

I'm currently having a revisit on the subject of periodicity of the periodic table, and I came across an issue that is kind of bugging me. If we take a look at the melting and boiling point trends of ...
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1 answer
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Work done in thermodynamic process

Here the official answer key given by Jee main is 48 Joules which makes no sense I believe that they just blindly found the area under the curve . if I am correct the answer should be 48+2*10(the area ...
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-5 votes
1 answer
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Reverse Engineering of Cooling Wallet [closed]

I am looking to reverse engineer the Cooling wallet scenario. For e.g. FRIO has created technology where their inner pouch soaked in water and it cools down and keeps it there for 45h (as per their ...
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2 votes
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Dissolution Thermodynamics - What is the standard state in units of mole fraction?

I have recently been working on a project that involves the correlation of mole fraction solubility using the Apelblat equation (in simplified form: $\ln\chi = A +\frac{B}{T}$), which can allegedly be ...
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1 answer
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Work done by gases on each other in the process of mixing them

I was wondering if gases, which are in the process of mixing, do any work on each other. I haven’t found many resources on this. We all know that gases, which have a higher pressure than their ...
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2 answers
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Explaining the process of boiling a liquid

as of right now, I am confused by the thermodynamic definition of boiling. It is stated that boiling occurs when the vapor pressure of a liquid is the same as the ambient atmosphere. Now suppose we ...
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3 votes
1 answer
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Why can't all chemist/IUPAC agree to make equilibrium constant as dimensionless?

I mean the gold book defines two terms as the equilibrium constant - the standard/thermodynamic equilibrium constant and generic equilibrium constant. To me, only the thermodynamic one seems correct ...
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1 vote
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Adhesion energy vs free energy of solvation

I am looking to compute the solvation free energy of Pt(111). Experimental data are still rare because the entropic term is hard to measure. I have found a paper where they use a QM/MM approach to ...
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How to calculate the temperature of a mix?

I'm trying to solve a problem but there is something im not quite getting. It says, if we mix 84.2 mL liquid water at a 15°C and 50 mL of 100% sulfuric acid at 25°C, What is the maximum temperature ...
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Vapor-Liquid Equilibrium and partial pressure of ammonia

I tried searching the forums for a similar question but I do not think it was entirely answered: Suppose I have a closed system in a container with solvent and a certain concentration of gas, say ...
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Expressing ΔH and ΔS using heat capacities and then using these to express ΔG

Essentially, I think I derived the correct expressions for ΔH and ΔS, but for some reason I can't combine them into the correct form of ΔG. Workings below:
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Can entropy of universe remain constant in a process where P and T is constant?

We know $$\Delta S(\text{univ})=\Delta S(\text{sys})+\Delta S(\text{surr})$$ at constant $P$, $T$. $$\Delta S(\text{sys})=\Delta H(\text{sys})/T$$ $$\Delta S(\text{surr})=\Delta H(\text{surr})/T$$ As $...
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What factors influence the upper size limit of micelle's?

Is there an inherent size at which micelle's cannot grow larger in volume? I have been trying to find a quantifiable method of measuring a size limit with all the variables that affect micelle ...
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1 vote
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Help in analysing dilatometer results

I need some help in analysing results for a dilotometer experiment. I did this experiment for the first time and don't have any prior experience in this field. The main aim of this experiment was ...
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How can you have standard enthalpy of formation of water at 298 K?

Firstly, I want to clarify in advance that im not good at this subject. Secondly, when i go through my chem book to search for thermodynamic data of water at 298 kelvin. I am able to find the standard ...
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2 votes
0 answers
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How to use DSC to differentiate first and second order phase transition?

The DSC trace below was recorded for a thermotropic calamitic liquid crystal. The heating rate was 5 $^\text{o}$C min$^{-1}$; a heating scan is followed by a cooling scan. Based on the previously ...
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Standard Gibbs free energy when all the reactants and products are at standard condition

I have read in my textbook that for a reaction $\Delta G=\Delta G^o-RT\ln Q $, where $\Delta G^o$ is the Gibbs free energy change when the initial concentration of products and reactants are unity. ...
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Is the formation of nitrogen dioxide spontaneous?

I was studying Thermodynamics from my Chemistry textbook (page 181-182, section 6.6 (a)). I have a question regarding the following text from my book. Now let us examine the following reactions: $$\...
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1 answer
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Can I take H = 0 at absolute zero

I am a 12th grade students making a reaction engine(includes state change, solvation also) on java, I was wondering can I take enthalpy(heat not change in heat) of a substance 0 at P(ext.) = 1, ...
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2 votes
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Prigogine vs. Bronsted and the minimum entropy production principle

I apologize for the length of this question that was asked here prigogine-bronsted but got no reply; anyhow, Bronsted's name is much better known among chemists than among physicists... Prigogine's ...
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What will happen in the volume occupied capacity of each gas when separator is removed? [closed]

Consider a situation where two gases occupying volumes $V_1$ and $V_2$ and having partial pressures $p_1$ and $p_2$, respectively, are kept separated in a rigid container. If the separator is removed, ...
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1 vote
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Difference between the specific heat capacity of potassium chloride solution and sodium chloride solution

I am curious about the difference between the specific heat capacity of a potassium chloride solution (KCl + water) and a sodium chloride solution (NaCl + water) - particularly the specific heat ...
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1 answer
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How to identify isochoric process from the problem's wording?

Problem 19 from NEET's Solved Paper 2013: The amount of heat energy required to raise the temperature of $\pu{1 g}$ of helium at NTP from $T_1$ to $T_2$ (in kelvin) is \begin{align} &\text{(a)}~\...
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3 votes
3 answers
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How do thermodynamic variables behave in reversible and irreversible processes?

I read this definition: reversible process is one which can be stopped at any stage and reversed so that the system and surroundings are exactly restored to their initial states. An irreversible ...
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2 answers
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Delta U is a state function?

Can we say $\Delta U$ is a state function? According to me, $\Delta U$ is not a state function. $dU$ is an exact differential and $U$ is a state function. Statement 1: Basic meaning of state function (...
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Is the maximum work done by voltaic cell per mole of reaction? [duplicate]

From the equation $w_{elec,rev}=-nF\Delta E$, and n = the number of moles of electrons transferred in the overall redox reaction, does that make the work per mole of the redox reaction? I am confused ...
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1 vote
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How to calculate vapor pressure of ethanol at given temperature?

The following is a part of the problem I am struggling with. I think what I need is a vapor pressure of ethanol at $\pu{25 °C},$ but I may be totally wrong. A reactor is charged with $\pu{60 bar}$ of ...
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What is happening when I dissolve styrofoam in acetone? (And should this change temperature)

I’ve completed a science experiment on endothermic and exothermic reactions in which I measured the temperature of solvents before adding solutes and measuring again. I found that dissolving styrofoam ...
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1 answer
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What is the relationship between the concentration of potassium chloride in water and its specific heat capacity?

I am curious about the effect that adding potassium chloride to water in varying concentrations has on its specific heat capacity. I have been unable to find any online information about this? ...
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Energy change of isentropic expansion of ideal gas

I'm trying to get a better grasp on dealing with different processes thermodynamic, and this one is giving me trouble. The differential of energy is given by $$dU= \delta Q + \delta W~.$$ I'm ...
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Does Boltzmann distribution refers to microstates or particle's probability?

I am reading about the Boltzmann distribution and I can't grasp the following: $$p_i = e^{-\frac{E_i}{k_B T}}$$ Is this the probability finding the system at a microstate with Energy $E_i$ or the ...
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4 votes
1 answer
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Ellingham diagram/graph for tungsten

I've recently come across one of the methods to form tungsten carbide($\ce{WC}$) from wolframite ($\ce{(Fe,Mn)WO4}$) by using carbothermic reduction which was supposedly one of the first methods for ...
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1 answer
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How do I calculate the maximum temperature of an exothermic NaOH reaction in water?

As the title suggests, let's say I want to make a 1 L 14M NaOH solution. For this I'd need: (14 mol/ L) x 1 L x (39.99 g / mol ) = 559.86 g NaOH(s) {solute} ~1 L H2O (approx) {solvent} The ...
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