Formation Definition and 509 Threads

Has anyone had experience with calculating the enthalpy of formation from DFT? I have had a few calculations with the planewave-pseudopotential method. What puzzles me is that in one case the agreement with experimental values is excellent, while another case was about 30% more stable...

. They understand the classical Schwarzschild radius argument for black hole formation. They have bare rudiments of special and general rel. I sound like an idiot saying "there's this anti-gravity" force that kicks in when the collapsing system gets really big. Any help?

Can anyone solve me these questions, please 1. A convergent lens has one 8 cm focal length. One places a 2 cm height object at 4 cm of his optical center. Find the various characteristics of the image obtained. 2. A divergent lens has one 8 cm focal length. One places a 2 cm height object...

Hi, I'm not good enough to contribute answers yet, but I hope to entertain you with questions. Practically all the Earth formation stuff I've read talks about the Earth being molton. That always seems strange to me. If I think of a space body without an atmosphere, I generally think of it...

There is a bit of data and literature that shows the standard heats of formation for various uranium compounds including UO3, U3O8 UF6 etc. However there appears to be nothing on ammonium diuranate which is one of the most common intermediate forms produced by precipitation. The ADU as it is...

Homework Statement A 75 g bungee cord has an equilibrium length of 1.20 m. The cord is stretched to a length of 1.80 m, then vibrated at 20 Hz. This produces a standing wave with two antinodes. Homework Equations I really am not sure how to approach this using an equation, tried to use...

Currently I am enrolled in college level General Chemistry course, and at this time we are working on a project to figure out the delta heat for formation of a specific reaction. The equation is this H2 + CuSO4(aq) ---> Cu(s) + H2SO4. We have gone through and determined the half...

What is the estimated value of the local star formation rate (SFR) and how accurately do we know this number?

Calculate the energy change for the formation of CaF2 (s) from its elements in their standard states and the following information: Ca (s) + F2 (g) -> CaF2 ? Ca (s) -> Ca (g) = 179.3 kJ/mol Ca (g) -> Ca+ (ion) (g) + e- = 589.9 kJ/mol Ca+ (ion) (g) -> Ca2+ (ion) (g) +e- = 1145 kJ/mol 1/2...

I realize that this is a chem prob, but I'm stuck with what I thought was a straightforward problem while studying for my physical chemistry exam. Homework Statement The standard molar enthalpy of combustion of solid phenol (C6H5OH) is -3054 kJ/mol at 298k and it's standard molar entropy...

A friend and colleague found a fossil and brought it into show me. It is a small leaf in a rock. He asked me how the rock was formed, but I couldn't say as I know nothing of such things. The rock is layered. You can see the various layers by looking at the rock edgewise. In fact, the edge is so...

My question is about the formation of a neutron star once fussion stops and it collapses. I recently saw a show about the life of a star and it said when gravity overcomes the energy released by fussion, the electrons are compressed toward the nucleus of the atoms and create neutrons. I...

What causes objects (such as leaves) in the pool to group at the edges?

The question I'm about to asked has probably asked before many times b , but I keyed in a "supermassive black holes and galaxy formation" in the PF search engine , and this question has yet to be asked: How can supermassive black holes be aid the formation of galaxies when they are suppose to...

Homework Statement Find the average bond enthalpy, εN-F, for NF3(g)→ N(g) + 3F(g) Heats of formation NF3(g)→ 1/2N2(g) + 3/2F2(g) -∆ƒHºm = 124.3 kj/mol 1/2 F2(g) → F(g) ∆ƒHºm = 79 kj/mol 1/2N2(g) → N(g) ∆ƒHºm = 472.7 kj/mol...

Homework Statement Hi, I've worked this out (I think) but would appreciate someone xhecking over my method. U 235 and U 238 found in ratio of 7.3E-3 to 1, but thought to have been produced equally (ie equal quantities) half lives are 1.03E9 and 6.49E9 respectively. Estimate time since...

So far i have found two theorise of how they form, the SSPSF shock wave model ,and the Density wave model, or they may form by a combination of the two. As i am not sure how old these theories are, i wonder if there are any new insights on the subject?

Hi, Hope someone here can help. I'm working on explanatory graphics on how nuclear fusion works, and how the elements are formed. In particular, I need to show how elements heavier than iron are formed. The obvious process is as part of a supernova explosion, but for the life of me I can't...

I Need the explanation of "The image of formation of black hole" Please Explain Me This

Question Statement: Would you expect the enthalpy change of formation of calcium carbonate to be higher or lower than that of magnesium carbonate. What I think: Calcium has a bigger radius than magnesium, hence I expect the lattice energy of MgCO3 to be greater than the CaCO3. I suspect...

Homework Statement What are the physical and chemical changes that occur when NaOH and Zn react.?Also how do this reaction differ from the reaction of Zn and HCl? Homework Equations ------------------------------------------------------------------------- The Attempt at a Solution...

I was curious as to how planetary type spherical bodies form. Specifically, I was curious as to how the gravity affects the nebulous particles moving within themselves just prior to a solid planetary body forming. Is it not true that gravity is essentially zero in the center of a planetary...

If something hit the Earth billions of years ago and caused a molten blob to be released from it,and this blob settled into a spherical shape,after vibrating a lot,could the moon still be vibrating because of a formation process like this?

I am puzzled about the formation of blackbody emission (Planck's law). Specifically, we know that such things like incandescent lamps, an electric arc in a gas at high pressure etc. produce a nearly blackbody spectrum of corresponding temperature. Does this mean that in these cases a nearly...

Homework Statement i did a lab calorimeter lab with 50ml 1.51M nh3 and 50ml 1.59M hcl yeilding nh4cl (aq) the deltaT was 8.6 degC second part is 100ml of h2o and 4.082g nh4cl deltaT was -2.8 degC Homework Equations how do i find deltaH per mole for each reaction?The Attempt at a Solution

When hydroxide ion is added to Mn(II) in aqueous solution, an insoluble white precipitate of manganous hydroxide, Mn(OH)2, is formed. If there is oxygen present, this material reacts with it to form manganic hydroxide, Mn(OH)3 Part one was easy because it wasnt a redox it just needed to be...

In an edition of the New Scientist it says: "The streams of water vapour and ice particles that form behind an aircraft, called contrails, are known to create cirrus clouds. These clouds can trap heat radiating from the Earth's surface and thus add to global warming" How big an addition to...

I don't believe the cloud formation by particles from space idea because why would they be doing this now (we'd have to be unlucky given geological timescales) and why isn't there evidence of this in the past.

In my textbook, it had 2Cu2+(aq) + 4I-(aq) -> CuI(s) + I2(aq) How does that work? First of all it's not balanced. It should be 2CuI(s). But how does CuI(s) form. It should be CuI+. The book did say excess 4I- was usd to remove Ag+ since it was talking about back titrations. But the...

Since in our proper frame of reference the fall of material into a black hole would appear to take for an eternity, would it not follow then that all black holes would appear as these instead? Would in fact all black holes appear this way? What if you have a small black hole and then have...

When i read "Alternative" i immediately thought "crackpots!", but then I read on and found out they're on to interesting stuff. http://www.physorg.com/news85310822.html

Hi Basically, I am doing an A level project, in which I am investigating impact craters. I am modeling this by dropping ball bearings into sand, and measuring the depth and width of the resulting crater. However, my results are quite unclear, and I would really appreciate some guidance...

I read in the book of world records that there are massive diamonds inside of some white dwarves. If this is compleatly true then how long after it's formation could a white dwarf start producing this massive diamond in it's core?

under what circumstances phenol forms phenolate with max yield

Hi, I have a question involving enthalphy of formation. I tried doing this problem but I couldn't seem to get the right answer. I was wondering if anyone here may please help me out. Thanks. Question: How much heat is evolved when 13.39 moles of CO(g) is burned in excess oxygen. 2CO(g) +...

I have no idea whether or not this is a ridiculous question, so I am just going to ask it. My question is based on the concept that energy must be added to ions to get them to form compounds (such as the formation of hydrogen iodide). Typically (or so my chemistry textbook says), the addition...

Here is my question in the formation of Schottky Diode: "Why does conduction band is lower than the original value in the semiconductor side?" And I think it is lower because the postitve charged donor ions provide a attractive force ,which makes the electrons in semiconductor more easy to...

I've google and read, but could anyone tell me how to find out the standard enthalpy of formation for any compound? :confused: thnx

OOPS I didn't see this forum I posted this earlier in the "Other Sciences > Chem." section...Sorry about that! My original post is below... Hey guys this is my 1st post here...Need help with a question that's been troubling me for a long time... A student determined experimentally that...

Hey guys this is my 1st post here...Need help with a question that's been troubling me for a long time... A student determined experimentally that 2.06 kJ of heat energy were released when 0.365 g of copper reacted with excess chloride. From these data, the enthalapy of formation of copper...

Hi, I am working on a project that involves molecules of water vapor, hydrocarbon and O2 being broken down by a laser beam (193nm) and ozone being formed as a result of that; and was wondering if anybody could explain the phenemenon to me (even briefly), or point me out to the right...

I need some heats of formation for a chemistry teacher I'm helping. If anyone could help me out that would be great. These are the ones I need: SO3-2 S2O8-2 OCl-1 Thanks again.

How do these come about, also what are the leading theories behind the formation of these objects?

Hello, I am new to this forum and guess what :P my first post is going to be a question, well, a few. Why do crystals form at low temperatures? What physics are involved with this? are there any articles on this subject (ive tried looking, but havnt found anything so far)? thanks!

What evidence do we have that stars are forming right now? Molecular clouds? why do we know that molecular clouds are where stars form? any other lines of evidence? i know this is a big topic so a few reasons or a good link would be a good start for me to understand this big topic thanks

When a cation and anion combine to form an ionic compound, the cation is usually written before the anion. I.e. NaCl But with some ionic compounds like sodium acetate, it is written with the anion acetate written first. i.e. CH3COONa Why like this?

I had a thought the other night when I heard that there is a super massive black hole at the center of every galaxy. My thought was is it possible that the big bang did not happen once trillions of years ago? Is it possible that every galaxy was created by its individual big bang from the...

In a recent theological discussion, I came to realize that there is a point in question regarding planet formation in the current model of the origins of the Solar System. The question itself is not theological, but has some theological ramifications. It goes like this: Planets are believed...

:confused: 1.) Is it possible for the number of neutrons and the number of protons to be equal? 2.) Is it possible for the mass number(nucleon number) and atomic number(proton number) of an atom to be equal? 3.) Is there any energy invovled in the formation of mixture? 4.) does...

In the case of nanoparticles is there any diffrence on the results (particle size and the other properties that are dependent on particle size) of two similer samples, one of which is annealed after pellet formation and the second sample is annealed in the powdered shape and then pellet is...