Thermo Definition and 299 Threads

Hi! I am reading Molecular Driving Forces, 2nd ed., by Dill & Bromberg. On page 53, example 3.9, we consider why energy exchanges between two systems from the point of view of the 2nd law. We consider two separate systems. Each has ten particles, and each particle has two possible energy...

Homework Statement I was asked to prove that (dP/dS)T (subscript T ie, at a constant temperature) equals κPV ("kappa"PV, or, isothermal compressibility x pressure x volume). By using the Maxwell relation -(dS/dP)T = (dT/dV)P I got an answer of -1/(alpha*volume) but cannot find out how to...

Question: in a bicycle pump the preasure increases from [p1 = 10^5] to [p2 = 30^5]. If the process is adiabatic ant the air starts at [T1 = 293 K], find the maximum temperature of the air in the pump. (Assuming air can be treated as an ideal gas) Attempt: So using the 1st Law and given...

Homework Statement A young engineer notices in her plant that 1-kg blocks of brick are routinely removed from a 800 ıC oven and are let to cool in air at 25 ıC. Conscious about cost-cutting and efficiency, she wonders whether some work could be recovered from this process. Calculate the...

Hey, guys. I am currently in a Thermo I class and have ran into a problem that has me completely stumped. I have worked in numerous different ways and anything I come up with doesn't seem to make since or be realistic. Here's the question: Two rigid vessels are connected by a small valve and...

I have this problem: Two (2) kilograms of Nitrogen gas at 600 K and 10 atm are allowed to expand such that they end up occupying three (3) times the initial volume and providing 50% of the isobaric work. mass = 2000 g temp1 = 600 K pressure1 = 1013250 Pa gasC = 8.3144621 n = mass/28.0134 =...

I attached the HW assignment. Its question number 2. I choose a control volume including the cooling stream from the lake and the fluid being condensed. I assumed with this CV that the heat generated was 0 and that the net Work was 0. Using these assumptions I solved for the mass...

Homework Statement Show that in a reversible adiabatic process, for 1 mole of ideal gas P1V1γ=P2V2γ Where, γ=CP/CVHomework Equations Listed above.The Attempt at a Solution Frankly, I don't really understand what I'm being asked to do.

Hi, I have my exam in a couple of weeks. And I get the jist of it. However their is one question that I am completely stuck on. Any help would be appreciated. Looking over a last years practise text for exam and I am having trouble with this. Cu(s) → Cu+(aq) + e ΔH = 602 kJ mol-1 Cu(s)...

Is it strictly true that an engine will be more efficient if operating in a hotter environment... e.g. your car is more efficient in the summer than the winter? Just going through thermo 1, not a HW question, but it just seems to be true to me because the simple Newton's law of cooling says...

Homework Statement A cube of Al (.1m x .1m x .1m with mass=.27kg) is placed on a large thermal mass maintained at constant 40 C (313 K).The cube is separated from the thermal mass by a .01m thick glass plate (.1m x .1m). If the Al block is initially at 10 C, how long does it take to reach a...

Homework Statement Consider a rod that is 1m long whose radius changes from 1cm at one end to 4cm at the other end in a uniform fashion. Assume that the end with r=1cm i kept at 0°C and that the end with r=4cm is kept at 100° C. Determine the temperature profile along the rod. One can assume...

Homework Statement 1 mole of ideal gas initially at 294 K is compressed adiabatically and reversibly from 0.83 atm to 10.0 atm. Calculate the initial and …final volumes, the final temperature, \DeltaU; \DeltaH; Q; and W: Assume that Cv = (5/2)R Given: n = 1 mol T1 = 294 K P1 =...

does this look right? for the quasistatic case you can use thermodynamics to find the temperature at any time, for the other case you have to use dU=dW and so on since its not quasistatic

Homework Statement Air is expanded in a piston-cylinder arrangement at a constant P of 200kPa from a volume of 0.1 m3 to a volume of 0.3m3. Then the temperature is held constant during an expansion to a volume of 0.5m3. Predict the total work done in the air. Homework Equations W = ∫PdV...

Homework Statement My question has to do with heating water to a superheated state inside a constant volume vessel. Given: A pressure vessel with a total volume of 36.77ft^3, is filled with 5 gal of water and heated from room temp. to a final temp. of 1100°F. Obvisouly the initial pressure...

My question has to do with heating water to a superheated state inside a constant volume vessel. Given: A pressure vessel with a total volume of 36.77ft^3, is filled with 5 gal of water and heated from room temp. to a final temp. of 1100°F. Obvisouly the initial pressure is atmospheric and...

If : The total energy of a falling rock = G.P.E. (mass x gravity x height) + K.E. (0.5 x mass velocity^2) But if a rock reaches terminal velocity (i.e velocity remains the same) but height keep decreasing, then surely Kinetic energy is remaining constant and Gravitational potential energy is...

Homework Statement A duct of length 5 m at 38 Degrees inclination to horizon with a cross section dimensions of 0.3 m X 0.4 m is carrying 2 kg/s of a heavy gas at 10C and 1.2 bars and delivers the gas flow at 50C at the end of the duct to a horizontal pipe section. i) Calculate changes to...

Homework Statement Consider a sample containing 2.35 mol of an ideal diatomic gas. (a) Assuming the molecules rotate but do not vibrate, find the total heat capacity of the sample at constant volume. nCv.= (b) Assuming the molecules rotate but do not vibrate, find the total heat...

Hello. I need help with some thermo basics. I can't understand the concept of constant volume compression/expansion. Please help me understand how it occurs. Also, I am not clear on how pressure is an intensive property. To my understanding it IS a quantity dependent on system size (eg...

Homework Statement Show that for a general (but simple) substance, c_{p}-c_{v}=-T(\frac{∂v*}{∂T})_{p}(\frac{∂p}{∂v*})_{T} where v* is the specific volume p is the pressure c_{p} is the heat capacity when p is const c_{v} is the heat capacity when v is const Q is heat T is temperature in...

Hi Can anyone direct me to the correct Thermo formula to solve the following problem. What is the time for water to heat up from 25'c to 75'c when placed in a 1000'c oven? Tnx Ilan

O_o. I know this is a really stupid question, but how the heck did the Q - W get to the other side of the equation? Shouldn't it be W - Q? I'm going to feel really stupid when I hear the answer, I'm sure, and I'm already done with the class so it's ultimately irrelevant, but I'd love to know.

Disclosure: I am studying biochemistry so my thermodynamics education is lacking and I'm likely misinterpreting some of these concepts (that's why I'm here for help). I have always had trouble defining some properties as either intensive or extensive. I understand that extensive are...

Homework Statement 1.A gas increases in temperature from 40 C to 120 C while increasing in volume from 1 m3 to 1:3 m3. Find the nal pressure, if the initial pressure is atmospheric pressure. 2.Estimate the length of time it takes for a 0.1 m x 0.1 m x 0.1 m block of steel to cool from...

Homework Statement Show that processes involving rapid chemical reactions are irreversible by considering the combustion of a natural gas (e.g. methane) and air mixture in a rigid container. Homework Equations Q_{in}+W_{e,in}-W_{b}=\Delta U+\Delta KE+ \Delta PE The Attempt at a Solution I...

Hey, i have a Thermo exam tomorrow, and I've been working through the textbook examples and problems, and i was wondering if anyone here had some helpful problems for me to work out or any general hints or anything. Our textbook is the 7th edition of moran shaprio thermo and the exam is...

Homework Statement A parcel of dry air is lifted isothermally such that its pressure decreases from 1000 hPa to 850 hPa. Calculate the change in specific entropy of the parcel. Homework Equations ΔS=n*R*ln(p1/p2) The Attempt at a Solution Using R=8.314 J/mol K p1=1000hPa...

Homework Statement A three-step cycle is undergone by 3.8 mol of an ideal diatomic gas: (1) the temperature of the gas is increased from 210 K to 550 K at constant volume; (2) the gas is then isothermally expanded to its original pressure; (3) the gas is then contracted at constant...

Homework Statement Hey, I was wondering if I could get some help verifying my answers for these general thermodynamics concept questions. Thanks! 1. A reversible reaction is at equilibrium at constant pressure and temperature if the free energy of the system ______________. 2. Heat...

This problem is from Callen. In the 1st edition it is 15.4-3. I am stuck on the last part of this problem. It also appears, in a slightly different form, in the second edition of Callen as problem 19.3-5. Homework Statement 15.4-3 Consider a small volume V within a two-component simple...

Homework Statement A cube of copper of mass 4 kg and initial temperature of 110 oC is set to radiatively cool in an environment of 100 oC. (Note: copper has an emissivity of about 0.05. Also, neglect conduction and convection as cooling agents in this problem.) The surface area of the...

Homework Statement Air at 300K(=T_s) flows over a flat plate maintained at 400K(=T_f). At a particular location on the plate, the temperature distribution in the air measure from the plate surface is given by T(y)=(T_s-T_f)exp[-22,000*y(m)]+T_f Q.Determine the conduction heat flux through...

Hey everybody! I'm in my Junior year of undergraduate Mechanical Engineering and am trying to figure out what direction to focus my studies (mainly what industry to focus my pursuit for next job/internship)... Does anyone know of any fields/industries where an engineer can utilize...

Derive the fundamental equations of thermodynamics for an open system containing a onecomponent fluid in terms of the intensive internal energy U = U/N, the intensive Helmholtz free energy A, the intensive Gibbs free energy G, and the intensive enthalpy H. For each of the equations write the one...

I'm trying to calculate the final pressure. I was given initial and final temperatures as well as initial pressure, expansitivy and isothermal bulk modulus. I was also told the volume is constant. Since volume is constant I figured dV=0 so in the formula dV=VβdT - VKdP it reduces to...

Thermo: Compressor--flowing system analysis Homework Statement A compressor takes 90 kg/min of helium at 120 kPa and 310 K and compresses it to 700 kPa and 430K. A heat loss of 20 kJ/kg of helium flowing is noted. Determine: (a) the work required by the compressor (kJ/kg), and (b)...

Hey I was given this problem: The moles of components of a gas mixture are given. The mole fractions and the apparent molecular weight are to be determined. The given properties are: The molar masses of He, O2, N2, and H2O are 4.0, 32.0, 28.0 and 18.0 lbm/lbmol respectively and there...

"Measured heat capacities of solids and liquids are almost always at constant pressure, not constant volume. To see why, estimate the pressure needed to keep V fixed as T increases, as follows. a)First imagine slightly increasing the temp of a material at constant pressure. Write the change...

Homework Statement Show that if a single-component system is such that PVk is constant in an adiabatic process (k is a positive constant) the energy is U = [1/(k-1)]PV + Nf(PVk/Nk) where f is an arbitrary function.Homework Equations Fundamental relation: U = [1/(k-1)]PV + Nf(PVk/Nk). State...

Hello everyone, Below is one paragraphe from my thermo textbook: Equilibrium for Ai but not for T (XiA = XiB but, for example : TA > TB). Thus, for U and S, we have a gap in relation to the equilibrium : UA = UAeq + \deltaUA,UB = UBeq + \deltaUB Ai is state variables such as V,l, ect. T...

Homework Statement In my book it says, "only if the transformation is reversible can we use dS=\frac{\delta Q}{T}", but I don't know why? I think even if it's not reversible we also use \delta Q=TdS to solve the thermo problems, don't we? I'm looking forward to your ideas, thanks.

Thermo Efficiency question! Homework Statement Figure P22.53 represents n mol of an ideal monatomic gas being taken through a cycle that consists of two isothermal processes at temperatures 3Ti and Ti and two constant-volume processes. For each cycle, determine, in terms of n, R, and Ti ...

i heard that fluid dynamics and thermo dynamics are the hardest subjects in mechanical engineering and physics, can somebody elaborate on this issue ?

Homework Statement Container 1 has a volume of 10 ft^3 and contains ideal gas at a pressure of a atm and temperature of 273 F. Container 2 has a bolume of 1 ft^3 and contains the same quantity of ideal gas at a pressure of 0.1 atm and temperature of 273 F. The two containers are separated...

Hi everybody, I've got a thermodynamics exam coming in a few weeks. I couldn't sit the exam when I took the subject 12 months ago because of work commitments so I'm sitting a deferred exam this semester. Trouble is I have forgotten most of it, and having difficulty getting help from lecturers...

suppose I have a pressurized container filled halfway with water and the rest filled with a noncondensible gas. In one case, I would open a valve at the top and relieve only gas, and in the other case I would open a valve at the bottom and relieve only liquid. If I relieve an equal amount of...

Homework Statement Hi there. I was trying to solve this problem from Callen. It says: In the vecinity of the triple point the vapor pressure of liquid ammonia (in Pascals) is rerpesented by: \ln P=24.38-\frac{3063}{T} This is the equation of the liquid-vapor boundary curve in a P-T...

Homework Statement rotational energy of diatomic gas (note : h = hbar) Er = h2/2I * r(r+1) , r = 0,1,2 ... it is (2r+1) fold degenerate find the partition function and hence the heat capacity at low temperatures. The Attempt at a Solution Z = ∑ g(Er) e-BEr = ∑ (2r+1) e-Bh2/2I *...