Formation Definition and 509 Threads

I have a chemical equation and the molar enthalpies of formation for its products, along with the total change in enthalpy for the reaction. With this I can easily find the total enthalpy of the reactants. In this case, there are two reactants and I need the molar enthalpy of formation of one of...

Sir, Ice starts forming in a lake at 0 degree Celsius, when the atmospheric temperature is -10 degree Celsius. If the time taken for 1 cm of ice to be formed is 7 hrs, what is the time taken for the thickness of ice change from 1 cm to 2cm? Can you please give a hint to solve this problem?

Could the process of star formation in a collapsing gas cloud transform the process of virialisation and ultimately promote the formation of a central black hole? Consider the following idealised and oversimplified scenario. Suppose a gas cloud massive enough to generate vast numbers of...

can u help me to explain the role of gravity in the equilibrium of stars in their production of enegry , and an explanation of the role of gravity in the formation of planets. thankssssssss

Has anyone ever formed water by manmade process? How is water formed and what conditions need to be met?

91. Write balanced equations to show the formation of each of the following compounds. Name the reactants in each case, and show clearly the removal of the water molecule. a) butyl propanoate b) propyl methanoate Answers: a) butyl propanoate- C7H14O2 = (CH3CH2COOCH2CH2CH2CH3)...

Write balanced equations to show the formation of each of the following compounds. Name the reactants in each case, and show clearly the removal of the water molecule. a) butyl propanoate b) propyl methanoate Im not exactly sure how to answer this question... below are pics of the...

I've been reading articles on star formation and would like to know what the Pre-main-sequence actually stands for. Since more or less each stage of the formation of a star have names what type of star are inclusive in the PMS? How can you point out a PMS star from a main sequence star?

Write balanced equations to show the formation of each of the following compunds: a) butyl propanote b) propyl methanote I am doing a horribly constructed independent learning course, they offered absolutly no information on this topic, and then asked me to solve this question.. I really...

I am looking for good information about the formation of earthquakes. My textbook is not very good and Wikipedia did not satisfy me. I know that someome might have a good site or article about this topic. Thank you. I will continue to search, if i find one I will warn you. Thank you! :biggrin:

what is the product formed when Br2 is added to 1-methylcyclopentane?

How are metallic bonds formed? Does it have anything to do with the merging of d orbitals to obtain a half full shell configuration or is it something else? Thank you for your time. -Scott

Ok, on this one I have no idea where to start. I could do all the homework ones, but have no clue even where to start on this. To me it seems backwards, but who knows. Here is the question: Calculate the standard heat of formation of acetaldehyde, CH_{3}CHO , given the following information...

For the following molecules and ions, indicate the obitals involved in bond formation. 1) SO2 The central atom is S, and it has 1 double bond with a O and a single bond with the remaining O. There is also 1 lone electron pair. Therefore, a S-O bond is sp^2-p while a S=O bond is sp^2-sp^3...

can anyone tell me how planets form and how we know that life can only exist in an environment where there is liquid water. is it possible that we only know how to observe or measure lifeforms we have previously encountered?:confused:

http://arxiv.org/abs/astro-ph/0510697 Authors: Rychard J. Bouwens (UCSC), Garth D. Illingworth (UCSC) Comments: 5 pages, 2 figures. Conference proceedings for The Fabulous Destiny of Galaxies: Bridging Past and Present, Marseille, June 2005 HST ACS and NICMOS data are now of sufficient...

I'm reading up on star formation and from what I've understood so far, is that protogalactic clouds with density fluctuations cool and then fragment after which, they fragment again into subfragments. Now do the density in these individual subfragments increase the temperature enough to start...

This question involves the following statement in Schutz, A First Course in GR, but you don't need to have a copy to answer it. He says that in the formation of a black hole from a supernova explosion, we should expect gravity waves of amplitude M/R, where M is the mass and R is the distance...

hello. I'm studying philosophy, I'm going with a scholarship in France. I'm very interested in physics, particularly in quantum physics, and universe formation, laws,etc. I'm not directly interested to find books, or get an advice what to read. i want to discuss some issues with someone that...

In a lab I work at at school we are trying to create aggregates of the lanthanide gadalinium along with carboxyl groups which are attached to a long (20 or so) carbon chain. The problem is we are getting polymers of lanthanides with carboxyls instead of a large number of universally sized...

When will the Last Galaxy be created?..are the Newest (detected) Galaxies part of an ongoing process, or is there is definate Closure to their Existence/Creation. And are there more or 'less' Galaxies being created at this present epoch?..or was there a definate period of 'MASS-CREATION' (I mean...

The CDM model predicts the existence of lots of dark halos without star formation. These are halos which did not attract enough baryons in order to set some kind of gravitational instability, which could lead to the further collapse of the baryons and to star formation (see, e.g...

http://arxiv.org/PS_cache/astro-ph/pdf/0506/0506156.pdf Title: Masers and the Massive Star Formation Process: New Insights Through Infrared Observations Authors: James M. De Buizer (1), James T. Radomski (1,2), Charles M. Telesco (2), Robert K. Pina (3) ((1) Gemini Observatory, (2)...

A hypothetical question: Say that Newton's constant G is increased a bit during the period between weak interaction decoupling and the time when photodisintegration becomes ineffective, and the helium is formed. (I.e. during the period when neutrons just decay). Would that give a larger or...

The formation of products is strongly favoured in the acid-base system: HX + B- <--- HB + X- ----> a) Identify the bases competing for protons. b) Which base is stronger? c) Which is the weaker acid, HX or HB? d) Does the K for this system have a large or small value...

AFAIK hydrogen was one of the first elements in our universe, i came to wonder, what conditions would prevent hydrogen from forming, and our universe consisting of only radiation?

The Following two questions are giving me the worst time. Maybe someone else can lead me in the right direction. Question 1: You unconsciously estimate the distance to an object from the angle it subtends in your field of view. This angle \theta in radians is related to the linear height of...

Note: This isn't an actual homework question, and I tried asking others (including teachers), but no one could answer it. Now, the heat of formation for sodium hydroxide is -425.6 kJ/mol (so it's exothermic). When you dissolve NaOH in water, the reaction is exothermic. But this is...

How would you calculate the standard enthalpy of formation of N2O5(g) in kJ/mol from the following data (all species are gases): 2 NO + O2-----2 NO2 ∆H° = –114.1 kJ 4 NO2 + O2-----2 N2O5 ∆H° = –110.2 kJ N2 + O2------2 NO ∆H° = +180.5 kJ Any help is greatly appreciated!

I was just wondering if somebody could check to make sure my logic is correct for this lab exercise. The setup is basically this: using an ophthalmoscope, a doctor can peer into the pupil of a patient to view the retina and innards of the eye. The opthalmoscope is a device with a built-in...

Got a question about the energy dissipated during the formation of hydrochloric acid, upon the reaction of hydrogen and chlorine (photochemical reaction). Whats the exothermic energy involved and the intensity of light needed to activate this reaction, in other words the activation energy. And...

:redface: How is White light form? I know that it is a combination of 7 colours...But just want to know how the 7 light with different frequencies merged?

i have tow questions from eth question list which I think will be present in this exam..Would you please tell me 1.when teh babies brain will be formed in mothers ? 2.if any, how a smoking mother would afftec her child's brain at that time ? Thank you so very much if you could offered me...

Dissolve a chloride into a water, add excess nitric acid, then pour silver nitrate solution. A white precipitate is formed. What's it ?

Has there ever been a hypothesis or theory propsed (current or obsolete) proposing that the rocky planets formed from gas giants whose ring system collapsed and combined with the core of the gas giant forming the bulk of a new rocky planet? Just wondering if this has ever been proposed or...

In ammonia, why the N atom is sp3 hybridized and not sp2 hybridized...since there are only 3 bondings... Also, in ethyne, that is H-C(triple bond)C-H...for the formation of 2 pi bonds, why it is the unhybridized 2px orbital and 2py orbital of each C atom overlap with each other? How about the...

Hi I've been reading a lot about esters and have the general idea but I am not sure about exact amounts of acid catalyst needed. say the following experiment was tro be carried out to form an ester R-C=O(O-R2) *X moles of R-C=O(OH) *10X moles of R2-C-OH *How much H2SO4 would be needed? i...

Hi all, I'm a sixth year student in Scotland hoping to go onto study astrophysics at university. Keeping with this i have chosen to do my project on the formation of craters from meteor impacts. I am wondering if anyone could direct me to a site or suggest some advice on going about this...

According to the big-bang model, it is assumed that when the universe was young enough (lets say z > 1100), the density fluctuations did evolve in the linear regime. Due to this fact, one can make use of simple linearized formulas such as the continuity, Poisson and Euler equations to model the...

how are lines of induction formed due to 2 horseshoe magnets that are placed side by side but no contact? Are there websites that would show me about it?

In the nucleus of a spiral galaxy the most stars are old population II stars, and there is no star formation (which occurs in the spiral arms). Why? Thanks.

Can someone tell me which is the favoured theory for planetary formation, core accretion or Gravitational instabilities, and if these are the only valid theories?

[FONT=Comic Sans MS] [COLOR=LightBlue] Okay, this is a general question.. i just read this thread (https://www.physicsforums.com/showthread.php?t=28343) and started wondering about it. THis planet is considered "young", and it is a million years old. SO, my question was why does planet formation...

Ok, a lens is held upright with a piece of clay. In front of it is a bulb, and behind it is a screen at the location of the image of the bulb. Now, what would happen to the image if the top half of the lens were covered by a mask? And what if the mask had a small hole in the center and were...

how is a black hole formed exactly from a neutron star or a white dwarf?? what is it? is it a star? is it defined as a matter?? and what happens when light gets sucked into it? there ought to be an increase in energy in it right? what happens to this energy?

stars are formed from gas clouds, these gas clouds posses potential energy and kinematic energy, they may also exhibit a density contrast, theory tells us that collapse of the gas cloud starts when PE overcomes KE, but i can find no explanation for the trigger to this collapse ,put another...

This is my first post, so I am going to get straight into a double barreled question that has been bugging me for a while. (1) How long does it take for stars to conglomerate around a general loci, in order to form a proto-galaxy. ? I ask this in the light of the most recent Hubble images...

http://www.spaceref.com/news/viewpr.html?pid=13330 To their surprise, the researchers found that in specific cases, the computer calculations suggested that the sphere would change shape dramatically. Frey said these special circumstances, called singularities, might ultimately reveal...

Hi. I was reading through my organic chemistry book and they had a little piece on carbonic acid. So CO2 reacts with water and produces carbonic acid, very nice, I read about this before. But now that I've been enlighted with organic chemistry and the idea of mechanisms behind every reaction I...

At standard temperature and pressure, what is the heat of formation of water vapor?