# 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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### Current and reversible heat in battery reaction

In the book Battery Technology Handbook by Kiehne  (Google Books) on page 21, equation (32): The reversible heat effect per time unit can be related to current flow, because each multiple of the ...
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### Calculate the energy in the form of heat (in kJ) required to convert 325 grams of liquid water at 20.0 °C to steam at 115 °C

Calculate the energy in the form of heat (in kJ) required to convert 325 g of liquid water at 20.0 °C to steam at 115 °C. Assume that no energy in the form of heat is transferred to the environment. (...
1answer
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### How to calculate dew point of air-water system

I want to calculate the maximum water holding capacity of air at a given temperature (as in $\frac{max\ mass\ of\ water}{mass\ of\ dry\ air}$ vs temperature) I looked up online and there are ...
0answers
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### Impact of pH? Change in Binding Affinity of protein-ligand complex based on pH and Kd?

When the $\mathrm{pH}$ was $5.0$, the temperature was $\pu{25 °C}$,the $K_\mathrm{D}$ was $\pu{5 μM}$, and [L] was equal to $K_D$, the protein(s) were half bound. Question considers half bound ...
1answer
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### Chemical Equilibria - Fraction Bound equation based on Kd, [R], [L], [RL], is actually an average?

Let's say 150 stem cells express exactly 150 copies of the same mebrane antigen X. While all differentiated cells express exactly 15 copies of X. To the cell mixture you add a large amount of 0.2 μM ...
2answers
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### Enzyme Kinetics - Given Km find substrate concentration at a certain velocity

From what I understand about the Michaelis Menten Model Km defines the amount of substrate required to reach half-saturation. 1/2 Vmax corresponds to Km on the x axis Generic formula is v = Kcat [...
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### why is white phosphorous given to have ZERO standard heat of formation [duplicate]

why is white phosphorous given to have ZERO standard heat of formation?? while it is well known fact that white phosphorous is highly reactive and is obviously less stable than red and black ...
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1answer
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### Temperature dependency of enthalpy H and entropy S [closed]

In textbooks, I often read that the temperature dependency of the enthalpy of reaction $\Delta_\mathrm{r}H$ and the entropy of reaction $\Delta_\mathrm{r}S$ can be neglected (in a limited $T$-range). ...
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### Hydrogen peroxide and carbon as hybrid rocket propellant?

I was thinking that a hybrid rocket could be made using hydrogen peroxide and activated charcoal or some other carbon source. Step 1: Decompose hydrogen peroxide to steam and oxygen, as in a ...
2answers
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### Cp vs Cv for liquid water @ < 4 °C

I'm looking at a textbook question (Engel & Reid, Thermodynamics, Statistical Thermodynamics & Kinetics, 4 ed, Q3.1) which states the following: The heat capacity $C_{\mathrm m,p}$ is less ...
1answer
44 views

### Calorimetry: Temperature Increase due to stirring of reactants

I am not yet in university, but I hear a common first-year chemistry lab/practical is to do calorimetry taking into consideration the small (and usually negligible) rise in temperature due to the ...
1answer
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### Change in Gibbs free energy vs. change in enthalpy

When learning about other thermodynamic quantities, like $\Delta H$, I was taught that this represents the energy absorbed or released by a system after the reaction has gone 100% to completion. For ...
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### Is it possible to boil a liquid by just mixing many immiscible liquids together?

In open air, when vapour pressure reaches 1 atm, boiling takes place. I read that if we add two immiscible liquids together, the total vapour pressure of the 'mixture' is close to $p = p^*_A + p^*_b$,...
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### Enthalpy change of gas expansion against constant external pressure

A certain mass of gas is expanded from $\pu{1 L}$ at $\pu{10 atm}$ to $\pu{4L}$ at $\pu{5 atm}$ against a constant external pressure of $\pu{1 atm}$. If initial temperature of gas is $\pu{300 K}$ and ...
2answers
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### Which substances have the highest/lowest enthalpy of formation per gram?

Which substances have the most extreme enthalpies of formation per gram at standard temperature and pressure?
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### Thermal conductivity and enthalphy data for nitrogen gas

I am struggling to find the data for thermal conductivity and ethalphy of nitrogen gas at reduced pressure (500 mbar). Most of the information is for nitrogen gas at 1 bar or above. Does anyone know ...
2answers
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### Is heating water endothermic?

So I got a problem recently which asked to calculate the amount of energy needed to increase the temperature of 200 g of water from 26 to 51 degrees Celsius. The value I got was 20900 J. So far I ...
2answers
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### Is Gibbs energy change during osmosis positive? If so then why is it spontaneous?

For ideal solution, μA=μA* +RT lnxA ln function is an increasing function, means that the higher the xA the higher the μA......(1) Now consider osmosis. From Atkins' Physical Chemistry Ninth ...
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### Calculate chemical potentials to find electrode Fermi level

I'm running some simple simulations of the semiconductor-electrolyte interface and I'm having a hard time figuring out the equilibrium condition. Can someone please help me with my electrochemical ...
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### Why a Differential Scanning Calorimeter (DSC), to measure thermodynamic parameters, has problems?

I want to use a Differential Scanning Calorimeter (DSC) to determine when my protein unfolds as you increase the temperature in a DSC machine. The machine is pressurised (to 3A) during the run, so ...
2answers
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### For Hess' law type questions, when do you take the inverse of the constant and when do you switch the sign?

For example, when you're given the enthalpy $\Delta H$ of a reaction and you want to switch that reaction around in order to add it to something else, you switch the sign. Furthermore, when adding ...
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### Why enthalpy of adsorption is negative?

I have already read Is adsorption exothermic, and if so, why? but it didn't answered my query. To illustrate, let's take a hypothetical vacuum space. In that space, there is a solid and a gas, the ...
1answer
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### What is the Gibbs energy of dissolving a solid in pure water?

I am calculating the Gibbs energy of dissolving one mole of solid glucose in pure water such that the final solution has a volume of one liter and a concentration of one mole per liter. I have three ...
1answer
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### Mixture of water, methanol and dichloromethane

If I have a mixture of 25 vol% methanol in water and I mix it with an equal volume of dichloromethane (which is miscible with methanol but not water) can I roughly say that both phases (i.e. water and ...
1answer
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### Is temperature of crystallisation same as melting point temperature for polymers?

Melting point tends to be a temperature range. Is it true that the temperature of crystallisation is the highest temperature at which the polymer melts and thus there is some distinction between ...
1answer
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### Heat of formation of aqueous H⁺

In my book it is given that by convention heat of formation of aqueous $\ce{H+}$ is taken to be zero. Heat of formation is energy released or absorbed when 1 mole of a compound is formed from its ...