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# 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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### Standard state conditions in thermodynamics

Standard state conditions for standard Gibbs energy change stipulate (among other conditions) that partial pressure of each gas = 1 bar. e.g. 2A + 3B = 4C + 5D (all gases) Then for standard Gibbs ...
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### Mathematical justification for Le Chatelier's principle

At equilibrium \begin{align} K &= \exp\left(\cfrac{TΔS^\circ - ΔH^\circ}{RT}\right)\\ ⇒ \frac{\mathrm d \ln K}{\mathrm dT} &= \frac{ΔH^\circ}{RT^2} \end{align} If enthalpy change is ...
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The vapor pressure of zinc varies with temperature as $$\log P(\pu{mm Hg}) = -6850/T - 0.755\log T + 11.24 \label{eqn:1}\tag{1}$$ and that of liquid zinc as $$\log P(\pu{mm Hg}) = -6620/... 0answers 73 views ### How to I find the equilibrium temperature in this problem? From Castellan's Physical Chemistry, chapter 12 [1, p. 276]: 12.18 At \pu{25 °C} we have for rhombic sulfur: ΔG_\mathrm{f}^\circ = 0, ΔS^\circ = \pu{31.88 ± 0.17 J K-1 mol-1}; and for ... 1answer 65 views ### Constant Pressure and Temperature during Phase Change One of the solution guides to a question I was working on said that pressure and temperature is constant for a phase change. I understand why temperature is always constant for a phase change, but don'... 1answer 122 views ### Application of Nernst Equation in Potentiometric titration of Fe2+ with Ce4+ It is well Known that to find E_{cell} during titration of Fe^{2+} with Ce^{4+} we consider 3 domains: Before Equivalance point , E_+ = E_{Fe^{3+}/Fe^{2+}}^o+\frac{RT}{nF}log\frac{[Fe^{3+}]}{... 0answers 30 views ### Software to predict equilibrium products in the ideal gas phase I'm interested in software packages that can answer the following kind of question: If I mix 30mol% N_2 and 70mol% H_2 together at 2 bar and 2000C, what is the equilibrium composition after all ... 1answer 65 views ### Boiling point elevation does not depend on the solute? [closed] I've recently carried out an experiment trying to measure the boiling point elevation of water after adding 5M of NaCl and KCl. Although for some reason, KCl solution started boiling around 90 degree ... 2answers 84 views ### Temperature measurement Consider some liquid in a beaker. I am measuring its temperature using a thermometer. When i put my thermometer's bulb in the liquid, the particles of the bulb gain the same kinetic energy as of the ... 2answers 38 views ### Spontaneity of an exothermic chemical reaction When the process is exothermic (ΔHsystem​<0), and the entropy of the system increases (ΔSsystem​>0), the sign of ΔGsystem​ is negative at all temperatures. Thus, the process is always spontaneous. ... 4answers 75 views ### Basic concept of the first rule of thermodynamics There is a cylinder-piston system with some gas in it, and let's say this system is a closed system. Say that the system is submerged in a large beaker of water whose temperature is 25\ \mathrm{^\... 1answer 28 views ### What is the the total heat extracted in the process? [closed] Since this is a cyclic process:- Change in internal energy=0. In the process C-A the work done W is zero, thus the heat Q is zero since it is an isochoric process. Next in the process A-B, I got the ... 2answers 48 views ### Temperature measurement using thermometer [closed] I have two samples of water – 'A' and 'B'. My thermometer measured them to be 90 °C. They both have different volumes. So, the kinetic energy of the particles of sample A and B is same or different? ... 0answers 53 views ### What is the degree of freedom of the calcium carbonate dissociation reaction? Question \ce{CaCO3} dissociated in a closed system according to the reaction:$$\ce{CaCO3(s) -> CaO(s) + CO2(g)}$$Assuming the reaction is in thermodynamic equilibrium, what is/are ... 0answers 37 views ### Identifying endothermic and exothermic reaction [closed] How can I know that a given reaction is endothermic or exothermic? I know that all combustion reactions are exothermic. But what about other reactions? In my school exam I was asked about whether the ... 3answers 2k views ### Are all volatile liquids combustible? I realized that liquids like petrol, kerosene and even perfumes are combustible when they are volatile. Could that be the reason why water is not combustible is because it is not volatile? Are ... 0answers 42 views ### Calculating thermodynamic quantities for hydrogenation of iron nitride HW#6.3 If the reaction$$\ce{Fe2N(s) + 3/2 H2(g) <=> 2 Fe(s) + NH3(g)}$$comes to an equilibrium at a total pressure of \pu{1 bar}, analysis of the gas shows that at \pu{700 K} ... 0answers 88 views ### Why can't calorimetry be used to measure fast reactions? As my previous post was a bit unclear and unspecific, I am reformulating it. First of all this is a question that I had while reading some concepts my book introduces, so this isn't a homework ... 2answers 82 views ### How to calculate the standard Gibbs free energy of formation of bromine vapor at room temperature? The normal boiling point of liquid bromine is \pu{58.2 ^\circ C}. At \pu{9.3 ^\circ C} the equilibrium vapor pressure of liquid bromine is \pu{100 torr}. From this data, calculate the standard ... 1answer 88 views ### Entropy changes during transfer of heat between two bodies Consider two metal blocks, one at 500K and another at 300K, they are bought to contact with each other until they reach a common temperature. Find the entropy change of each object and the total ... 1answer 210 views ### Relation between First Law of Thermodynamics and Ideal Gas Law Thermodynamics has always been a tough thing for me. There are lots of assumptions in this subject (those assumptions, I know, are necessary, I know the science of thermodynamics is a very practical ... 0answers 26 views ### Reaction between chlorine gas and oxygen at 600 degrees Centigrade Chlorine gas will not normally react with oxygen gas directly at STP. However, would the two react at standard pressure and 600 degrees Centigrade? 1answer 84 views ### Thermodynamic vs kinetic basicity [closed] I'm writing something related to basicity and came across few papers that distinguish thermodynamic and kinetic basicity. "In particular, the study of hydrogen bonding (H-bonding) within proton ... 1answer 50 views ### Entropy for a closed system [closed] Case -1 In a free expansion of an ideal gas in a region or container, we cannot trace a pressure-volume path since the pressure, temperature and volume of the gas fluctuate unpredictably when the gas ... 1answer 65 views ### I was told that the more exothermic the solution, the more soluble the salt. Is this statement wrong? I was also told that$$\Delta H(\text{solution}) = \Delta H(\text{hydration}) - \Delta H(\text{lattice E})$$However, for \Delta H(\text{solution}) to be exothermic, it has to have a negative value ... 1answer 34 views ### Boiling point elevation and liquid solutions \pu{1 L} of an aqueous solution of urea having density \pu{1.06 g mL-1} is found to have elevation in boiling point \Delta T_\mathrm{b} = \pu{0.5 °C}. If the temperature of this solution is ... 0answers 18 views ### Computing enthalpy of formation of dissolved gas from its enthalpy of dissolution Provided that I know the enthalpy of formation \Delta H_f^0(X_{g}) of a substance X in gas phase and its enthalpy of dissolution \Delta H^0_{sol}(X) in the same conditions, considering that the ... 2answers 85 views ### How to derive this temperature-pressure-specific volume relationship? (for isentropic, adiabatic, ideal gas flow)$$\frac{T_x}{T_y} = \left(\frac{p_x}{p_y}\right)^{\frac{(\gamma-1)}{\gamma}} = \left(\frac{V_y}{V_x}\right)^{\gamma-1}$$where V is the specific volume, ... 1answer 127 views ### Finding the isotherm with given minima Get the temperature of the isotherm for water for which the local minimum is at \pu{100 Pa}. Use the values of a and b of water. My approach In the van der Waals equation, set$$\frac{\...
I've seen that it's defined as $h_0 = h + \frac{v^2}{2}$, where $h_0$ is the total enthalpy per unit mass. I can see that the $\frac{v^2}{2}$ term probably has something to do with kinetic energy, but ...