Applied Chemistry

I know that entropy is a measure of molecular disorder of a system. But how come that two different molecules have two different entropy-values? Example: The entropy of Hydrogen H2(g) = 131 J/(K·mol); Helium He(g) = 126 J/(K·mol); Fluorine F2(g) = 203 J/(K·mol); ... and so on. (Standard values at 298K and 1atm) For me it would seem that the only factors (at inducing "randomness") to take into consideration would be size and #atoms/bonds in the molecule, but I can't seem to pick a trend... Anybody can help me here, I have some guesses myself....????

Hi all. First let me say that I am new to Chemistry and after viewing the fountains of knowledge on the subject I have ultimate faith that someone will be able to help me. I have recently seen these "Flameless Heaters" used by Military and the like to heat their MRE's. According to what research I have been able to do, the pads used Iron Powder, Magnesium, Salt and Water. Apparently they will heat up to 220 degrees! I have an idea for an emergency heater using the same principal. My question is this: What amounts of each of these materials (more specifically what ratios) would you anticipate I would need to used to cause the desired reaction? Thanks so muc…

what is the partial pressure of nitrogen in a container that contains 2 mos of oxygen, 3 mols of nitrogen, and 1 mol of carbon dioxide wehn the total pressure is 900 mmHg?

Today, I learnt about the reaction and did a displacement. Mainly the displacement reaction, A+Compound with metal C-----> C + Compound with A Where A is more reactive than C and it displaces it. What if A is less reactive than C? I found that some reaction still undergo where most of the reaction. I found that magnesium displaces iron(II) sulphate very fast. The reaction involve a large amount of heat released and even steam was produced. Why? Last, do the non-metals displace similarly? And is hydrogen more reactive than potassium to displace metals?

Hey guys, Im stuck on some work ive got to do for later this week, heres the question: chlorine gas is passed over phosphorus it is found that 6.28g of phosphorus yield 10.54g of a product. Work out the empirical formula of the product?. So i think ive got to work out the ratios to get the formula. Cl + P -> PCl Then i tried to work out the number of moles of each but it didnt get me any clear ratios. Can anyone help? Thanks, Jacky Logan

if so, i would be interested in knowing the results you obtained in the practical exam that was held today. thx! -mak10 P.S: I am talking about the Cambridge board AS chemistry practicals that was held today.

I need help! I have an absolutely terrible analytical chemistry teacher, and I don't understand a thing. I am feeling really discouraged. Can someone please give me a detailed run down of how to write mass balance equations for known and unknown concentrations. THANKS!!

Some neo-nazi has claimed that I miscalculated. Can one of you guys check this to make sure I did not make an error? His calculation. According to the Merck Index, dozens of conversion tables and as many online sources that I could find I have come to the conclusion that Zyklon B (Hydrogen Cyanide or HCN) was sold in tins that containd 1.134kg of HCN. According to the Merck Index, above 25 degrees celsius HCN readily forms the gas. According to the Merck and other sources, the lethal concentration of Zyklon B or HCN needed to kill within minutes is 300 parts per million (ppm) which is in fact 300mg per liter of air and because of its vapor pressure, it can easily…

May I ask a few questions related to chemistry? 1.Do all reactions have an equilibrium time? 2.For a slow rate reaction, the time for equilibrium is far long than the higher rate, right? 3. Does water dissociate into hydronium ion and hydroxide ion a kind of reaction? I find that the constant does not imply the water is in equilibrium at STP. 4. Aluminium oxide is bonded with strong ionic bonding. Is it possible to dissolve in molten ionic compound? ( In fact, I know there is no molten ionic compound but please imagine ) Thanks for reading this./

I was wondering wether or not what I believe to be the explanation for pH is correct; In pure water there is 2 H atoms with a total mass of 2. Coupled with teh mass of 14 it becomes 14/2 or 7 a neutral pH.

This isnt a homework question, just something i was wondering while flipping through my chem textbook, i was looking at a chart and it shows the heating process of both pure methanol compared to 75% water and 25% methanol when pure methanol is heated, it just starts going up and a pretty uniform rate.. but when the mixture of water and methanol is heated, it goes up slowly for around 2.5 seconds.. and then starts going up much faster than pure methanol, why is this? is there a.. building-up-energy time or something when heating up mixtures, or is it only in this example? thanks in advance =)

I live in North Texas, and have been ordering all my chemicals from skylighter.com The only problem I'm having is paying astronomical shipping for 4 extra pounds of potassium nitrate and what not that I don't need. I've asked United Nuclear, and they've told me they're not aware of any warehouse in North Texas, or anywhere in texas that sells basic chemicals. Does anyone here know of one?

Hi Everyone, I'm new to this forum and I've come to get help with determining amphipathicity of small molecules. What parameters are used to define amphipathicity? How is amphipathicity characterized or rated? Thanks for your help Liz Murray

Hey guys. I'm hoping someone here can help me out. I've been looking at my halogens and have been paying close attention to my bromine ampoule. I did some calculations and figured out that if all of the bromine vaporized, the pressure in the tube would be 99 atmospheres. heh. It would go boom pretty violently. However, what I can't seem to figure out is how to calculate the pressure present inside a tube when there is still liquid present. I.E. at about 105 degrees Fahrenheit, what would the pressure inside the bromine ampoule be? (That would be about 313.7 K). The cylinder has a total volume of about 24.333 mL, and there is about 4.5 mL of liquid bromine insid…

Why is sodium chloride said to be very hard? We can break it easily. Can't us? Moreover, how can people make graphite? Is making diamond more difficult or making graphite?

hiya, my names karen and im in serious need of your help. i have a chem project that involves doing a powerpoint on einstein and planck and what they contributed to the history of the atom. I am having some problems with finding annimations. i need annimations of anything having to do with either scientist and the atom or what happens inside the atomic bomb, or anything else u think may be useful. I dont really know what im doing here, and i apreciate any help u can give me Thankies

Hello, I need help with making a density column. I need four liquids that I can put into a container, shake, and have them all return to there separate layers. I have corn oil, and water. I have tried alcohol, other oils, and household cleaners, everything I can possibly imagine in my house but everything mixes with either the corn oil or water. I do not know what else to do, I am desperate. I cannot use anything flammable or too toxic. Please help. Thank you, Brianna

Hi, as a physicist, I'm learning chemistry from scratch!! What exactly is pH in molecular term? (I remember it was something like logarithm of number of hydrogen ions?) And how does the pH value of an organic mixture affects the oxidation of a moiety in the mixture, say, silver nitrate --> silver oxide? Thanks, Jack.

One of the reasons given for the impracticality of large-scale usage of fuel cells to power vehicles is that it takes more energy to crack the hydrogen from a water molecule than any energy gain from the usage of said hydrogen as a fuel. My questions are: 1. Is that true? All you have to do, I think, to seperate the hydrogen from water is run an electrical current through it. Then again, my knowledge of chemistry is shamefully inadequate. How do they seperate hydrogen from water, anyways? 2. Aren't there some chemical reactions that release hydrogen? I remember reading about simply mixing sulfuric acid with iron filings, and that releasing hydrogen (I think that w…

does anybody know any experiments which could get me on tv and get a free conical flask, because i could send the experiment to brainiac 2 and if they pick me ill get to go on tv and win a sort off trophy which is a conical flask attached to a wooden board

Hey Recently got in stuff like explosives smoke bombs and such. So please tell me the ratio for smoke bombs. how much sugar and KNO3 Thnx LP Aspirin

Heya im 17 and about to start thinkin bout Uni interviews. I wanna do chemistry at oxford. ne tips of ne books or research i shud do before i plan it out???? thanx

I'm not sure if this should go to the electronics, but since this involves chemicals I think chemistry is a good place for this. Recently, I've been wondering about electric ignition (especially high explosives are something you don't want to light with a match). The only useful electric ignition what I can think of is nickel-chrome wire (its resistance grows as current increases so it burns). I don't think it's used too often and that some compounds can be ignited quite easily with only 1,5V. Sadly, I can't think of any. Suggestions?

how do you work out electron config? like the 1ps2ps thingos thanx Phoenix

I was just wondering is there a general formula to work out bond angles? What are all the major components that determine bond angles? and bond lenghts? Cheers