Formation Definition and 508 Threads

I know the general accepted theory to the birth of our solar system. One or more nearby stars went supernova and the shock waves caused our gas cloud to collapse forming our solar system. However, i wanted an opinion from those with more knowledge on a hypothesis that seems to make some sense...

The wake is made because the inertia forces in the system ,right? So if i have low Reynolds number the inertia forces are negligible and the flow doesn't separate ,right? So In every low Reynolds number the flow doesn't separate (no wake) but low Reynolds number also indicate a viscous flow...

What is the reaction mechanism for 1,3-dibromopropane + 2Na ---> cyclopropane? Thanks :)

Hi, I'm scratching my head over the statement from my textbook which states when determinant is non-zero, the set of vectors blah blah is a basis for r^3. That does not make any sense to me because I know when a row of zeros in a matrix occur; the determinant is zero (through Gaussian...

Can anybody explain how this inverted icicle could have come to be formed ? This mug of water had been sitting outside for a few days, last night the temperature in Edinburgh dropped to below zero, and this morning I saw that this ice stalagmite had formed. There was no source of dripping...

We know that the interference pattern forms even when photons (or electrons etc.) are sent one at a time. The photons only land on the fringe parts of the screen and not the dark part - as if directed by some underlying information about where they are supposed to go. So far so good...

I'm very confused about how metal hydrides form. I'm looking at PCI plots and I see what's happening, but I have no idea why it is. For instance: "Molecular hydrogen is dissociated at the surface before absorption; two H atoms recombine to H2 in the desorption process." Why does this...

I've taken basic college physics and chemistry courses where I learned about entropy and thermodynamics, and I can tell you that I don't know that much :) That's my background. I understand that entropy is a description of 'randomness' and possible 'states'. When I wash my hands with soap...

I just recently came across this idea, outlined in http://arxiv.org/abs/1005.3497" ). I've looked for some discussion here, but couldn't find any, so I thought I'd start one (if I missed some previous discussion, I'd appreciate a link). The basic idea is simple: to probe transplanckian...

Hello everyone; I am a new member and have little formal hard science ed, but have read many pop science books by Sagan, Hawking, and others. In light of this fact please try to formulate answers with this in mind... NO MATH SPAMMING ALLOWED lol My question has to do with the...

Suppose that we have an ellipsoidal shell of particles, all initially at rest in some frame, which are going to collapse to form a black hole. Since the cloud has a nonvanishing mass quadrupole moment Q, and Q is varying with time, we should get gravitational radiation. First let's consider...

At certain concentrations of energy, there is the possibility of particles with mass forming. How does one measure "concentration of energy": by the wavelength? Or energy density? At what concentration will this occur, and why?

Hi. This is currently an academic question - I don't have a 'spare' motor to risk at present :) Would NOx catalytic converters become unnecessary on a 'spark' engine if only relatively cold air was made available at the intake? My thinking is that NOx formation needs high high peak temps and...

Homework Statement How much energy, in joules, is released when one mole of helium-4 nuclei is formed from its individual protons and neutrons? Homework Equations 2p + 2n ----> He-4 (p is proton n is neutron) The Attempt at a Solution Book sucks at explaining...

I'm trying to find some information about models of star formation (just out of curiosity). I only have a basic knowledge of text-book physics and calc, so it's hard to get started. In particular, I'd like to know how the theory is tested. The only prediction of Nebula theory that I can think...

Homework Statement I am trying to calculate the gas formation volume factor for a reservior, however I am stuck when trying to find the value n - number of moles for a gas to plug into the equation to find Bg, this is what I know; Bg (gas FVF)= volume of gas at reservoir conditions /...

Homework Statement Enthalpies of Formation. burning methane in oxygen can produce three different carbon-containing products: soot (very fine particles of graphite), CO2 (g), and CO2 (g). A) Write three balanced equations for the reaction of methane gas with oxygen to produce these three...

Hi, Could you please explain me how to predict the rate of formation of frost around a pipe carrying cryogenic fluid if the relative humidity is known? I am not able to make any assumptions as frost is porous. Is experimental analysis the only solution to this problem ? Can it be solved...

Hello every one I hope I'm in the right place to ask this question :) well , have you heared about Dr. Emoto's ? http://www.is-masaru-emoto-for-real.com/" my friend were in US last year , and she was joining some one who provides her by these info. when she told me , it was my 1st...

I would like to know if anyone else has seen this (photo below). I put a tray of purified water in my freezer and by the time it had half-way frozen, inch long ice shards at about a 45° angle had formed, grown right up out of the surface of the water. Can anyone point me to an explanation of...

Hello! I have a geology question; a subject which I know next to nothing about. Regarding tectonic plates, I heard someone suggest that when there is oceanic trench formation, it is always accompanied by mountain/hill formation. The websites I have looked at say that there MAY be mountain...

So I was reading through a textbook and came across the term 'close encounter' but no definition or explination of what it means. From what I can make out, I would assume it's referring to asteroid interaction with young galaxies and the role in forming galaxies and stars but this is all...

standard entropy of formation ?? Homework Statement the standard entropy of formation of magnesium is 32.7 J/mol k , That of oxygen gases 205.2 J/mol k at that magnesium oxide is 26.9 J/mol k . A) What is the entropic energy change when 25 grams of magnesium are burned inexcess...

the standard entropy of formation of magnesium is 32.7 J/mol k , That of oxygen gases 205.2 J/mol k at that magnesium oxide is 26.9 J/mol k . A) What is the entropic energy change when 25 grams of magnesium are burned inexcess oxygen at 25 celsius ?? B) Does the burning of magnesium in...

G'day. i'm a 2nd year Aero engineer student from Australia. I've had this question on my mind for the past few days now and can't seem to find much material on it. i was just wondering how the lightest elements (hydrogen and some helium) managed to come together in the center of the solar...

i did an experiment the other day where i split water into hydrogen and oxygen but i used a silver anode and cathode when i turned on the batterie the silver one i think the anode start to corrode( one the one that oxygen forms on) is this making silver oxide when this happens?

Homework Statement An alpha particle is bombarded on 14 N. As a result a 17 O nucleus is formed, and a particle is emitted. This particle is a: (a) neutron (b) proton...

Using Methane gas as an example (CH4 gas), explain why one can not assume the heat of combustion is the reverse of the heat of formation. I can't find a decent answer to this anywhere.

Can someone explain to me the fundamental understanding of why, when two hydrogen atoms for example, release energy when they form a covalent bond? I can't seem to comprehend. Here is my reasoning, please see if this makes any sense of I am simply going in the wrong direction, I would really...

Homework Statement The number of vacancies in a metal increases by a factor of six when the temperature is increased from 800K to 1000K. Calculate the energy for vacancy formation assuming that the density of the metal remains the same over this temperature range. Homework Equations Nv= N...

Homework Statement The standard enthalpy of formation for liquid water is -285.8 kJ / mole. Which of the following could be the standard enthalpy of formation for water vapor? A) -480.7 kJ / mole B) -285.8 kJ C) -241.8 kJ / mole D) +224.5 kJ / mole Homework Equations The...

Why do we need helium for star formation?

Apparently, in the early universe, stars were massive - ranging up to about 500 solar masses. Furthermore the metallicity (elements other than H, He) in the early universe was effectively zero with only hydrogen, helium and trace amounts of lithium. Apparently, stars could reach large masses...

Homework Statement Hi everyone. So I've already worked out delta H to be 57.88 kJ, T is 298K and I've been given a value of 29.94 for lnK0. Now I need to calculate delta S but think my numbers are too small to be doing it right...? Homework Equations 1.) delta G0 = -RTlnK0 2.) delta...

Homework Statement The question involves a HI could in the ISM with an observed 21-cm emission line. I'm asked whether formation of molecular Hydrogen is likely. Homework Equations Not entirely sure The Attempt at a Solution First of all, I should say that this is a...

Hello!:wink: May I ask for a little assistance in filling in the gaps of my understanding? :S I understand that the current large scale structure of the Universe is thought to be the result of early fluctuations in density which have been stretched out in the expansion of the Universe. I...

Nuclear reaction leading to formation of C^14 ? Hello. I've got two questions from the NPRE class. One of them is to estimate how old the certain wook piece contained some amount of C^14 is. I solved it. The real question is the second one which is " Write down the nuclear reaction...

Just got back from Lanzarote and was walking through a recent (300yr old Timenfaya) lava field. Very little rain in 300 years so it's more or less like it started, I guess. A great landscape to investigate the way volcanic landscapes develop. What I couldn't understand was the structure of the...

Homework Statement If the focal length of the concave lens is -7.50 cm, at what distance d_o from the lens should an object be placed so that its image is formed 3.70 cm from the lens? What is the magnification m produced by the concave lens described in above? Where should the object be...

Write formation reactions at 1 atmosphere pressure and 25°C for each of the following substnaces: Mercury (I) chloride solid Nitroethane (CH3CH2NO2) liquid I have absolutely no idea how to do this. If anyone can help show or explain to me how to solve this, I'd appreciate it

Homework Statement Using the enthalpies of formation given below, calculate ΔH°rxn in kJ, for the following reaction. 3NO2(g)+1H2O(l) -> 2HNO3(g)+1NO(g) NO2 (g): 33.10 kJ/mol H2O (l): -285.83 kJ/mol HNO3 (l): -174.10 kJ/mol NO (g): 90.29 kJ/mol Homework Equations dHrxn =...

Hi, I'm trying to understand how exactly a black hole fits into the evolution of red supergiants, especially in terms of a timeline. I understand that when the core of the star collapses, it reaches a point where the neutron pressure overcomes it's gravitational force and this deceleration...

Hello. the main question/doubt that I have is about the possibility of image formation through parallel projection [I'll explain in detail what I mean by that]. To make myself clear, I will start with a different question and connect that to this. + Consider a small rectangular box of a...

Quick question: why are the standard heats of formation 0 for pure elements?

For example, if we have 2-butanol, a compound with a secondary \alpha carbon and I reacted this with HCl and NH4Br I would get 2-bromobutane (via nucleophillic substitution), but how would I determine whether this goes via SN1 or SN2 to achieve this? Now, if this was 1-bromobutane, I know...

Is it common for rocky planets to form closer to a star and gas planets further? Why or why not is this?

I'm having trouble with this particular Heat of Formation problem. Question: One mole of CH3COCH3 produces -1788.9 kJ of heat when burnt. Delta Hf (H2O liquid) = -285.5 kJ Delta Hf (CO2 gas) = -393.5 kJ Find the heat of formation (Delta Hf) of acetone [Answer = -248.1 kJ/mol]...

What is the chance of planets forming from gas clouds without a star? has anyone calculated this? are they more likely to form than stars? could there be billions of rogue planets floating arround our galaxy?

Basically, I need confirmation on the heat produced when four mole of H2O is produced from Hydrogen and oxygen gas. I'm getting something ridiculous, basically saying that the temperature goes up to ~4000 degrees C. What I'm doing is using Hess's law to find the energies of reaction. H2 and...

Homework Statement Ozone can be prepared from molecular oxygen by subjecting oxygen to an electrical discharge. The standard free energy of formation of ozone is +163.4kJ/mol. a) write the chemical equation for the formation of ozone. b) what sign of the entropy change for this...