Thermodynamics Definition and 1000 Threads

Homework Statement The first excited state of the helium atom lies at an energy 19.82 eV above the ground state. If this excited state is three-fold degenerate while the ground state is non-degenerate, find the relative populations of the first excited and the ground states for helium gas in...

In thermodynamics when can we say that ΔH = ΔU?

Homework Statement We're told to show the attached equation, (partial P/partial V) at constant S = that big mess. Homework Equations dE=TdS - PdV The Attempt at a Solution lol just went in circles with the commuter and permuted rules. I have no clue how to end up where I'm supposed to be.

Homework Statement Hellooo, so this is the question that i have: A 0.5-m3 rigid tank initially contained a saturated liquid-vapor mixture of water at 140 °C is now heated until the mixture reaches the critical state. Determine the mass and the volume of liquid before the heating process...

Spontaneous negative entropy reactions can occur when the internal energy decrease is greater than the negative dS*T. dG=dU-dST is spontaneous if dG is negative. The moon is receiving at least 1E8 J/s from the loss of rotational energy from the Earth's water and air. A lot more rotational...

Homework Statement [/B] Homework Equations $$W=P\Delta V$$ $$\Delta U=nC_v\Delta T$$ The Attempt at a Solution . [/B] The gas is slowly heated. The temperature increases and the pressure increases as well. But since volume increases, the increases in pressure is nullified. The process is...

Homework Statement 10g of water at 0˚C added to 100g water at 50˚C Homework Equations Qhot+Qcold=0 Q=mcΔT Q=mL Σmc(Tf-Ti)=0 The Attempt at a Solution So I understand this problem, but I'm not sure when I am supposed to use Q=mL, L being the latency, I think. So with the problem mentioned you...

Homework Statement Two rigid containers, A and B, contain the same type of ideal gas and are connected by a thin tube which has been fitted with a valve. The initial pressures of the gases in A and B are P_1 and P_2, respectively, whilst the initial temperatures are T_1 and T_2, respectively...

Homework Statement In an experiment, 1.1kg of aluminium is heated to 92 degrees Celsius it is then dropped into 0.5kg of water at 12 degrees celsius. Find the final temperature of the mixture. (Cw= 4200JKg-1Celsius-1) (Cal= 880JKg-1Celsius-1) Homework Equations Qal = Qw The Attempt at a...

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...

THE PROBLEM: A steam engine's boiler completely converts 2638 g of water at 83.7 °C to steam at 195.4 °C. The steam, at a constant pressure of 3.28 Pa, expands by pushing a piston of radius 9.4 cm a distance of 8.3 cm. What is the change in internal energy of the water-steam system? MY WORK...

Homework Statement I am trying to understand the the following derivation: Cv = (qv/ΔT) = (ΔU/ΔT) \\ Cv = (∂U/∂T)v \\ dU = CvdT The Attempt at a Solution [/B] So here is what I understand so far. I understand that heat transfer q and temperature T are related by a direct...

Homework Statement 2 boxes containing the same number of moles of 2 ideal identical gases with the same adiabatic index (this is given as gamma), at the same initial temperature Ti but with different volumes, V1 and V2 are brought together. Find the maximum mechanical work that can be obtained...

Okay so after reading various books on sign conventions for work I am told by my teachers that in chemistry,work done on the system is positive while work done by the system is negative while in physics it's the exact opposite I only use the former convention And modify the first law of...

Homework Statement Okay, so these are usually pretty easy for me to understand, but this one doesn't make sense. 10 kg of water in a piston cylinder arrangement exists as saturated liquid/vapor at 100 kPa, with a quality of 50%. It is now heated so the volume triples. The mass of the piston is...

Homework Statement Two adiabatic vessels containing ##n## moles of mono atomic and diatomic gas respectively are connected by a rod of length ##l##, cross sectional area ##A## and thermal conductivity ##k##. The surface of the rod is insulated. The initial temperatures of the vessels are...

My question is what is the difference between ΔE and ΔU. Because I see both equations 2 and 3 interchangeably . But then I see equation 1. So there has to be a difference between them since they are using both symbols in one equation. I thought U was internal energy while E was total energy...

Hey guys, I have been wondering about this for a long time, and I can't seem to reach a solid conclusion. If temperature of an object is related to the movement of its atoms, then is it true to say that a moving object have a higher temperature?

I was studying zeroth law from MIT Courseware (http://ocw.mit.edu/courses/physics/8-333-statistical-mechanics-i-statistical-mechanics-of-particles-fall-2013/lecture-notes/MIT8_333F13_Lec1.pdf). On page 2, it is mentioned that equation I.4 can be simplified using equation I.5 by cancelling the...

Homework Statement Two well-insulated rigid tanks of equal volume, tank A and tank B, are connected via a valve. Tank A is initially empty. Tank B has 2 kg of Argon at 350 K and 5000 kPa. The valve is opened and the Argon fills both tanks. State 2 is the final equilibrium state. The temperature...

Why do we always see the claim that an isentropic process for a system is adiabatic and reversible? The change in entropy for a process is the sum of the entropy transfer accompanying heat and the entropy production. The entropy production term is always at least zero, and the transfer term...

From what I understand, in the Carnot cycle summing qi/Ti for each step results in zero, thus indicating a new state function, entropy = qrev/T. But since dE = 0 = q+w, then q = -w, and looking at the equations derived from the cycle summing wi/Ti for each step should also result in zero. So why...

I was reading Thermodynamics by Herbert Callen. In the first chapter he makes the following statement. 'The basic problem of thermodynamics is the determination of the equilibrium state that eventually results after the removal of internal constraints in closed composite system.' Then he...

In order to explain the change in energy of an ice cube removed from a refrigerator and placed on the kitchen counter, I consider it as a closed system (can exchange only energy but not matter). For the first law of thermodynamics, ∆U = Q+W. I'm pretty sure that the sign of Q is positive due to...

Hi Guys, A question that I've been mulling in my mind over the last few days, is it is practically possible to make a low pressure 'turbine' system at atmospheric pressures? I was looking at a low-pressure stirling engine, and wondering if the same thermodynamic principles would equally be...

Hi folks, This is a question about how to calculate entropy change when there is a temperature change involved. I got the correct answer to this, but I don't actually understand why it's correct..! Any help is much appreciated. Homework Statement One mole of liquid bromine is heated from 30...

If so, why do people use the word "energetics"?

I'm a newbie (obviously), but I just read this recent paper describing an "experimental realization of an autonomous Maxwell’s demon" (along with this review). I think I understand the general concept of Maxwell's thought experiment well enough (from a layman's perspective), but I'm having...

Hello, I have a very basic question about the expansion of the Universe and it could be that I'm being very stupid here: if the universe is expanding into the empty surroundings as the red shift evidence seems to demonstrate, then surely the universe must be doing work on the surroundings like...

So I have a question regarding the specific heat capacities in thermodynamics. In general the specific heat capacities for a gas (or gas mixture in thermo-chemical equilibrium) can be expressed as, ## c_p = \left(\frac{\partial h}{\partial T}\right)_p \qquad \text{and} \qquad c_v=...

Homework Statement Consider a rectangular isolated(non-conducting) chamber as shown below. The chamber is divided into three compartments. The wall separating A and B has negligible mass, no friction and is conducting, while the wall separating B and C has negligible mass and friction and is...

I was reading a bit about comrpessible flow and I came upon a problem, there's a diffuser which has air at Ma=0.9 at its inlet and the air comes out at 0.65, how should I go about finding the ratio of the inlet and outlet areas? I know It's related to this equation but I'm unsure about how...

I was going through a worked example in book "Concepts in Thermal Physics" by S.J. Blundell and K.M.Blundell. The example talks about measuring viscosity of a gas between two coaxial cylinders. Homework Statement Two vertical coaxial cylinders. Outer cylinders is rotated by a motor at constant...

This is not a homework problem. I want to relay a statement made by my professor. From his online script: "0th law of thermodynamics: If two subsystems I,II are separately in thermal contact with a third system, III, then they are in thermal equilibrium with each other." He stated this in...

Hi everybody, I am trying to build a small model which basically should be able output "mass flow of water vapor as a function of time" given following inputs: - initial mass liquid water m_l_0 [kg] - initial temperature of liquid water T_l_0 [°C] - initial pressure p_0 [Pa] - heat added as...

Hi There, Im studying thermodynamics at the moment and there's one statement about nozzles that I just haven't been able to understand. In my mind when a fluid exits a nozzle it would have a higher pressure than the inlet. Could someone please explain in what sense the pressure of a fluid drops...

Homework Statement For my physics IA, I am finding the specific heat capacity of water-solute mixtures and finding how the specific heat differs from that of just water alone. I have the mass of the mixture, for example baking soda and water was 914.75g and changed 175.8 degrees Fahrenheit in...

I wonder why we can find temperature (or pressure )when the other property value is given.Lets say we have a rigid tank, which contains 50Kg of water at 90 degree celsius. If we look up the thermodynamics table, we can find the saturation pressure 70.14 kpa and definite liquid and gas specific...

Homework Statement [/B] You are asked to calculate changes in internal energy, entropy, heat transferred and work done for each of the following process. Also you are asked to calculate "the latent heat for the isotherm in the figure". We know the a and b parameters which characterize the VdW...

Homework Statement For a rigid, impervious, closed tank - The volume of tank is filled with 70% water and the rest is with air- The initial temperature of the tank is 20 °C, and the absolute pressure is 1 bar. - What would be the final pressure if we raise the temperature to 200 °C? Homework...

Hello, Can u please explain how to convert a PV diagram to a TS diagram in thermodynamics. Thanks in advance

I'm learning about Maxwell relations of Thermodynamics, but it's difficult for me to find more books about this in Vietnamese. So, I want to ask you about some english ebook about this. Thanks a lot!

Figure P6.95 provides steady-state test data for a control volume in which two entering streams of air mix to form a single exiting stream. Stray heat transfer and kinetic and potential energy effects are negligible. A hard-to-read photocopy of the data sheet indicates that the pressure of the...

Homework Statement In my lecture notes(beginner thermodnyamics), we just got introduced to the first law(DeltaU=q+w) and two scenarios. One at constant volume which yields the equation Delta U = qv. I understand that The second scenario is at Constant pressure and it says that At constant...

I came across an equation used in one of the forums from a few years ago. Found here: https://www.physicsforums.com/threads/calculate-how-long-it-will-take-for-the-ice-to-melt.531908/ I am researching a similar topic into melting ice and using it as a cooling solution. However when i came...

Homework Statement My lecture notes says that Work is the transfer of energy by means of a force acting on an object/body. What about heat energy? Does work also need to be done to transfer heat energy from hot object to cold object? Say if i drop a hot metal into room temp water. The metal...

Good afternoon. You are a student of the career of physical I am 'm like someone aids with the second section (II) the following problem because I do not understand much. Thank you very much. Problem: Considering that the effects of pressure variation with height are due only factor hydrostatic...

When doing constant volume calorimetry, the enthalpy can be calculated as follows: ΔH = ΔU + Δ(PV) ΔH = w + q + Δ(PV) ΔH = PΔV + q + Δ(PV) and at constant volume: ΔH = q + VΔP which I've then see people rewrite using the ideal gas law as follows: ΔH = q + (Δn)RT where Δn is the change in...

I've read back and forth in my chapter and tried consulting with my forumla sheet, but I cannot seem to find the correct formula. I bet I am looking at this question wrong, but I am fairly sure I need to use the -100 kJ for something to find the final volume and pressure , along with the given...

Lets say we have T1. From a reservoir 4000K, Q is added and that makes the temperature T2. How do we calculate the entropy generation in a process like that? Isn't it Sgen=S2 - S1 - (Q/T) But which temperature we will use in the (Q/T)? T1, T2 or 4000K?