Homework Help

Mode note: moved to HW help ——— Suppose that by some artificial means it is possible to put more electrons in the higher energy state than in the lower energy state of a two level system (this sort of situation occurs in a laser, for example). Now it is clear that this cannot be an equilibrium situation, but nevertheless, for the time that the system is in this strange state we could, if we wished, still express the ratio of the populations in the upper and lower states by some parameter we can think of as an effective temperature. (i) Show that for such a population inversion to exist, the effective temperature must be negative. (ii) Imagine I have elect…

Show that the thermodynamic properties of an assembly of N three-dimensional harmonic oscillators are the same as those of an assembly of 3N one -dimensional oscillators. I can easily imagine this, but how do you actually prove it?

An array of N 1D simple harmonic oscillators is set up with an average energy per oscillator of (m + 1)hf Show that the entropy per oscillator is given by S/N = k[(1+m)ln(1+m) - (m)ln(m)] Comment on the value of the entropy when m = 0

Note: a Unit is ((ΔA/Δmin)/(6220 M -1 cm -1)) X 106 μM/M X 3 X 10-3 L An enzyme sample contains 24 mg protein/mL. Of this sample, 20 microliters in a standard incubation volume of 0.1 mL catalyzed the incorporation of glucose into glycogen at a rate of 1.6 nmol/min. Calculate the velocity of the reaction in terms of the following: A)micromoles/minute B)micromoles/liter/minute C)micromoles/miligrams of protein/minute D)Units/milliliter E)Units/miligrams of protein Of this sample, 50 mL were fractionated by ammonium sulfate precipitation. The fraction precipitating between 30 and 50% saturation was redissolved in a total volume of 10 mL and dialyzed.…

Quick Questions - Bold ones are the ones I literally have no clue about. Questions: 1) The area:volume ratio is significant for cells because? 2) The advantage organelles give cells is? 3) stomach lining cells contain a large number of ribosomes and Golgi because? 4) A student has observed an amoeba and drew it. If you are correcting this illustration and notice that they drew chloroplast. Do you remove marks or not? Explain.

Please help me out on this. I need immediate answers if thats possible. I'll really appreciate any help. This query is from a friend who emailed me: The experiment was basically to find the percentage purity of three different brands of iron tablets. I did this through titration with potassium permanganate. I also had to do colorimetry with different concentrations of the iron solution and with ammonium thiocyanate (makes solution go red). I also had to do colorimetry changing the thiocyanate concentration and by keeping the iron concentration the same - this would allow me to find the order of reaction. However, i was unable to get these results and so i have had to …

i reacted h2o2 and copper sulphate ,what i got was a murky green solution with bubbles being formed should this be so?if so can you point me to some law or theory which may tell me why..thanx to all in advance.

In school we did a lab where we oxidized ethanol and buthanol.Both gave vinegar after the reactions were complete.The acohols were oxidised with potassium dichromate and sulphuric acid.I have no idea what the acid is for and why did buthanol give vinegar.Can someone help me?

so like you have this sun and my teacher is like do a science report and im in 5th grade and he is mr. sould if u no him so i am doing my report on how the sun works.. wich i thought it wud be super easy but it is like so so so so hard this is wut i have ok so like u hav big bang and then everything is hydrogen.. and it has a super small mass. then gravitrons that make up all matter in the hydrogen make the hydrogen come together in big gass clouds called nebulas then the nebulas come together more and pressure goes up... and i gess as pressure goes up heat does to? i dont understand this cuz wen we lerned about spheres they said the thermospher…

Prove without using a calculater that cos36 -cos72 =1/2

basically i need a some credable fact and figures on what Acrylamide is and how it can effect your body, any papers, test research, would be very useful plus if you have any information, can you paste me a link or something like that A.S.A.P. thanks

hi im doing a science fair project and was wondering if anyone had info on the effect of electricity on plant growth. please help i could realy use it.

How do I find the correlation and regression for this linear graph. X: 0 , 100 , 200 , 300 , 400 , 500 , 600 , 700 , 800 , 900 , 1000 Y: 20 , 19 , 18 , 18 , 17 , 16.5 , 16 , 15 , 14.5 , 13.7 , 13 The ones lined up are the coordinates. Anyone can guide me as to how to find the answer?

I'm just a little stuck on a chemistry homework question at the moment. The question is about the use of cast iron cookware with acidic foods (such as fruits) resulting in iron(II) ions being ingested. And the question asks for a balanced ionic equation showing the formation of iron(II) ions in an acid solution. I know that the iron could oxidise to iron(II) ions and lose 2 electrons, but I can't think of how to show it in an acid solution. Do all I need to show is the oxidation half equation? Or is there something more, and if so what is it? Any ideas?

1) If you were experiencing hunger and wanted a peach from a bowl. Explain how the outer and inner stimuli are incorporated in your act. Stimuli is like gibberish to be Sorry for bugging you guys all the time

I have to make a solar system model for school, and I have to put the kuiper belt and asteroid belt in with it, I have no idea how to put the belts in. Also I have a set that has styrofoam balls and the planet stick out of the sun with wires. Also What could I use to make the belts?

We had a 100 questions about microscopes and there are some I am unsure about or I don't know. I will provide my guesses so you know I atleast tried to complete this, I just want to know if they're wrong or right and if wrong what the right answer would be. Thanks ! These questions are all regarding Light Compound Microscopes Q: Under which magnification (low, medium or high) is an image brought closest to the eye. A: High (guessing but I want to be 100% sure) Q: Which magnification would be best suited for scanning several objects? A: Low Q: Which magnification provides the widest angle of view? A: Low Q: Why is it easier to locate objects using …

Vic, a new member, sent me a PM asking these questions so I've started this thread in Homework Help for him. Vic asks: 1. Does the movement of earth around it's own axis, and around the sun, and gravity on earth, has an effect on, and explain why people walk in circles when totally lost in the wilderness ? 2. Will this always be true, and what do these circle patterns look like ? 3. If one locks a car's steering wheel in a straight position and keep driving, will you end up in or near the place you started from ?

Climatology Class..what are the effects to the seasons if the earth were tilted 35 deg and also 90 Seems like at 35 the poles would be warmer in summer and colder in winter the northern hemisphere would have less daylight hours At 90 there would be no seasonal changes...Any suggestions....

Hello SFN I got a problem concerning an experiment conducted in chemistry. We're going to submit an paper on this experiment by Monday, help is needed if this is to be fulfilled. Alright, the experiment we conducted was to examine an enzyme-catalysed reaktion through spectroscopy. The reaction is: Pyruvate + NADH + H+ -> Lactate + NAD+ We measure the absorbancy and it's change for the solution at the wavelenght 340 nm. That done, we're going to make a few calculations, this is the problem since neither I nor anyone I've talked to in my class can help me with these calculations. The subject hasn't been covered in class. The calculations are: (Be…

I know i can't change the title but i solved the problem i was looking for originally and need help with another... The question says to use an integrating factor to solve: x(dy/dx) = y + (y^2)x The problem comes at the very last part to find v' and v because of the y^2 term. The factor i'm using is: y = v*exp(-integral[-1/x]dx) where the -1/x is the term infront of the y when you divide by x and bring it across. Any pointers would be great. Thanks.

Basically we just have to write a page on what you think the most important quality of a scientist is. I have began and decided to write about skepticism. I jotted down all I could think of about why this is an important value of scientists, but it fails to meet the page-length standard. Could someone maybe give me an idea or two as to why it is?

I am having trouble doing these two problems. They are about finding the pH in solutions. Here they are: a) 1 liter of 0.1M acetic acid (pKa=4.7) to which has been added 75 ml of 1M NaOH. b) 1.0 liter of 0.1M glycine hydrochloride (pKa values are 2.3 and 9.7) to which has been added 100 ml of 1M NaOH. The pH must be determined for these problems. Any help would be much appreciated. Thank you.

Hi poeple, I would like to know the chemistry about Iodine vapor stain phosphatidylcholine in TLC experiment. What compound was formed? Thanks

I need some help with these how would you apporach them to answer it any hints: 1) whether two solvents will mix or which will sit on the top? 2) how to prepare molar solutions? 3) finding errors in transcribing results? 4) what are serial and non-serial dilution and what they are used for? Pls help thx