Chem Definition and 424 Threads

Homework Statement What is the approximate molal concentration of the solute pure ether? Kb is 2.02, normal boiling point is 37 degrees Celsius. Homework Equations ΔTb= Kb * m ΔTb is the change in boiling point temp. Kb for ether is 2.02 m is the molal concentration which I am trying to...

Hello everyone , I'm a medical student from Bulgaria and I'm having problems understanding the following : In a thermodynamical system the change in internal energy is: ΔU=T.ΔS - p.ΔV + Ʃ μ.ΔN μ is the chemical potential that one particle of a given substance would add when being added to...

I have a few questions about applying to REU programs. I've heard that some schools are a lot more selective than others...but how would you know which ones are the hardest/easiest to get into? I mean...I want to apply a some safeties (even getting into these will probably be difficult for me)...

I am finishing my BS in Chemistry, minor in Materials Science, looking to go to grad school as a MS in Physics. In the past year, I've struggled a lot with what graduate school to go to, and decided on Physics. I did this because in Chemistry, I learned all about applications of physics in...

Homework Statement From Atkins Phys. Chem 9th Ed, Ex6.5a: Dinitrogen Tetroxide is 18.46% Dissociated at 25 deg Celcius and 1 bar in the equilibrium N2O4(g) <-> 2NO2(g). Calculate K (equilibrium concentration) at a)25 deg. C. b) 100 deg. C. given that ΔH(standard of reaction) = +56.2 kJmol^-1...

I'm currently applying for various graduate schools in both physical chemistry and condensed matter physics. My undergraduate degree is a double major in both fields. I'm curious about what the differences between the departments (and, to an extent, fields) might be. In terms of research...

hello all i need to build my own vacuum chamber any references i build one but it is not working ... want your help and experience in it

Hello, I am a junior in a ChemE program right now and it is a lot more physics than I had imagined. I have some affinity for physics and my calc is strong, I am handling the coursework but I enjoy my chemistry classes much more than my Chem E classes. If I were to switch to chemistry I would be...

So this problem was a part of my homework and I did the whole thing but apparently I got it wrong. Could someone point out what's wrong with my work? Question:A compound contains only C, H, and N. Combustion of 35.0mg of the compound produces 33.5mg CO2 and 41.1mg H2O. What is the empirical...

Homework Statement The following data were obtained for the analysis of soil for vanadium content in mg/g using two different methods. Do the two methods yield essentially the same results? Method 1 Method 2 26.30 26.22 26.43 26.32 26.28 26.20 26.19...

Homework Statement The following set of analyses represent concentrations of chloride in blood serum (meq/L): 103,106,107,114. One value appears suspect. Determine if it can be rejected at the 95% confidence level. Homework Equations Mean Standard Deviation...

I am currently learning about stereochemistry in my O-chem class. I just have a few questions that I were running through my head. I know there are a lot of questions here, but they're not HW-related at all; my prof. just taught the lecture and I have had these questions on my mind. 1. How...

the question asks me to balance the following equation C2H3NO + H2O ---> C2H8N2O + 2CO2 i attempted to balance it 2C2H3NO + H2O ---> C2H8N2O + 2CO2 i can't get all the oxygens to be equal, if someone can show me how to do this last step, id appreciate it also can one use...

Hi everyone (hopefully I posted this in the right section), I know very little about graduate schools since I was pre-med for a long time, but only a few months ago realized I'd rather go to graduate school. I was hoping someone could help me figure out which programs in graduate schools to...

In short I'm a junior transfer with 1 year left to do my undergrad degree (constrained by time but mostly $). The physics major was too spread out for me to complete (since I only got to mechanics/EM last year); I chose chem because of the possibility of taking pchem. My math is Calc I-III and...

I'm a third year planning to graduate 1 semester early. Last fall, I took 18.5 credit hours and worked 2 jobs (paper delivery and research assistant). I was pretty wasted by the end of the semester. Subsequently, I got depressed the following spring semester and had to drop down to a part time...

Hello! I've just completed this homework problem but got ALL answers incorrect. I really thought I knew what I was doing so I'm kind of surprised. Could someone help point out what I had done wrong? Homework Statement Ag2CO3, is considerably more soluble in hot than in cold water. At 20 °C...

This question is pretty straightforward, but I just can't seem to find the answer.. What is the reason that electrons only exist in shells and never between them? A hint that was given to me was to "think about quantum energy". I was thinking because if they wouldn't exist in shells, then...

So, I only just finished my first year of college but I really want to major in Chemical Engineering. It's something that feels right. I started looking into minors and was wondering if anyone could tell me anything about a ChemE major with a Biochemical minor. Such things as what kind of jobs i...

Human blood gives rise to an osmotic pressure of approximately 7.7 atm at body temperature, 35.9 Celsius. What must the molarity of an intravenous glucose solution be to give rise to the same osmotic pressure as blood? ------------------------------ I use the equation ; P=MRT if that's...

The van't Hoff factor for KCl is i= 1.85. What is the boiling point of a 0.50 m solution of KCl in water? For water, Kb = 0.51. I have the equation which i believe is (Delta Tb)= Kb x m x i ?? m= molality... = .50 m Kb is given 0.51 i is given 1.85 I have to have 5 sig figs...

Homework Statement Im having some problems with some oxidation and reduction mechanisms. I am not sure if I am doing them correctly. Homework Equations 1. O=C=O + CH3-MG++I- 2. Acetone + NH4+, Na+ H3BCN The Attempt at a Solution 1. I break one of the bonds from the oxygen...

I took the first part of the college-level introductory chemistry classes (it's CHEM 1211 here). I took it a long time ago - 2002. When I took it, I didn't pay attention, it's a miracle I passed the class at all. And now I need the second part of the class. I'm worried that I'll be missing...

Question 1: Step 1: 2NO2 (g) + 2SO2 (g) = 2NO (g) + 2SO3 (g) Step 2: 2NO (g) + O2 (g) = 2NO2 (g) The reaction is found to be first order with respect to NO2 and SO2, what is the slow step for this reaction? 1. First step 2.Second step 3.Not possible to determine Question 2 and 3...

Homework Statement What volume of solution is needed to dissolve 1.0 mol of a strong base such as KOH to make a solution whose pH is 12.5? Homework Equations KOH_{(s)} \rightarrow K^{+}_{(aq)} + OH^{-}_{(aq)} pH = -log[H_{3}O^{+}] The Attempt at a Solution I'm not going to...

Homework Statement What is the solubility product for copper(I) sulfide, Cu2S, given that the solubility of Cu2S is 8.5 × 10-17 M? Homework Equations Cu_{2}S \leftrightarrow 2Cu^{+} + S^{2-} The Attempt at a Solution Set up the equilibrium constant expression: K_{sp} =...

Homework Statement Last week in organic chem lab, we were provided with an H NMR spectrum of an unknown compound with the formula C7H5NO3. I'm not terribly good at analyzing these spectra, but I've managed to figure out that I'm looking at 4-nitrobenzaldehyde. The only thing that's bothering...

Question: There are ___ orbitals in the third shell. 25 4 9 1 I picked 4... but the answer is 9... How did they come up with this?

Homework Statement When aluminum reacts with chlorine how much heat in KJ is released on reaction of 5.00 g of Al for the following reaction: 2AL (s) + 3 CL2(g) ----->2AlCl3 (s) delta h = -1408.4 Homework Equations The Attempt at a Solution Is it right if you start...

Homework Statement The question is.. In which of the following atoms is the 3s orbital closet to the nuclues... Br,Cl,At,I first off how are those atoms in the 3s orbital? I thought the 3s orbital where Na and Mg?

I am not understanding this def from the following paragraphs... The book says... The vibrational energies of an atom are said to be quantized, that is the possible ernergies are limited to certain values... If a vibrating atom changed energy, say from 3hv to 2hv (from the equation E =...

I am only a high school student so take some pity, I have an exam tomorrow and am trying to teach myself the method. But alas, not working >.< Could someone please answer them for me with working? My teacher kind of rushed over this and I didnt really understand: Q1) The pH of a mixture...

Homework Statement During a combination reaction such as.. P4(s) + 5O2(g) = P4O10(s) : DeltaH = -3010.. And for the decomposition reaction... P4O10(s) = P4(s) + 5O2(g) DeltaH = 3010 Questions 1. Is it true that for any combination reaction that Enthalpy will be neg, and...

For example cobalt, rhodium and iridium. I know that Co(II) and the Co(III) ions have a coordination number of 6 and that Co(II) is more common because cobalt is usually more stable in the 2+ oxidation state but when it coordinates NH3 ligands the 3+ oxidation state becomes more stable. Is this...

Homework Statement Any hints would help a lot for any question 3. Nuclear fuel pellets consist of a spherical core of radius R1 of fissionable material of thermal conductivity kn that generates an energy per volume S. To more easily handle this radioactive material, each pellet is encased in...

Homework Statement Use the “virial equation of state”. Measurements for Ar gave B = -21.7 cm3/mol and C = 1200 cm6 /mol-2. Assuming that Ar is a van der Waals-type gas, what are the values of “a” and “b” in the corresponding van der Waals equation of state Homework Equations PV= RT(1+...

Hi All! I ran across a homework problem ans am confused by the question. here it is: For a certain process at constant pressure, ∆U = − 225 kJ and +52 kJ of expansion work is done. What is ∆H for this process and does the volume increase or decrease? I know that ∆U=q+w and therefore...

I'm a freshman currently, and I just blatantly overestimated the difficulty of this class, and I didn't really treat it seriously. The teacher put intentionally tricky questions on the exams and I ended up failing them, and I'm feeling pretty bad about the whole situation. I intend to go into...

Hi Guys, I wanted to know if there are videos available to watch and learn the basics of Chemistry. It has been a while (high school) and I am in college now. I am taking "Chem 3A" at Fresno State (CSUF): "CHEM 3A. Introductory General Chemistry (4) Prerequisite: G.E. Foundation B4 (except...

As I am starting to think more about college and what career I want to major in I am questioning what engineering I would be most comfortable with and would like the most. I'm also even questionign if engineering in general is what I would want to do for the rest of my life. I wanted to now...

I took Pre-Ap Chem and got through it extremely easily. The only question is where to go from there. I can take AP Chem or Biochem if I want to stay in that area, which I do. I think I'm majoring in some form of Chemistry. I know the AP Chem teacher (she was my Pre-Ap teacher, too) and she says...

I decided to take Chemistry this term to see if I liked it or not. I thought it might not be too bad since I'm a math major (taking multi-var. calc right now) and am generally pretty good with problems involving calculation and formulas. However, whenever I have a midterm in chem, I always...

I started doing organic chemistry lab a few weeks ago and the instructor is an evil bastard when it comes to marking lab reports. We've 2 reports to do per week and I spend at least 6 hours on each report but only manage to get 60%. I can't be wasting all this time on a single class. Are there...

Homework Statement Calculate the factor by which the volume and the diameter of a balloon would increase as it rose from sea level and 20 degrees celsius to the stratosphere at 40km. Homework Equations PV=nRT The Attempt at a Solution I don't think I have enough information to solve?

Homework Statement You are titrating 30.0 mL of .3 M CH3NH2 with .15 M HNO3 Kb = 4.4 x 10^-4. Calculate pH: -initially -after 10.0 mL of acid has been added at the half equivalence point at the equivalence point when 70 mL of acid has been added.Homework Equations not sure. . . The Attempt...

Alright. I'm a pre-med so my science classes are really important. Unfortunately for me, I'm taking 18 credits and Bio + Chem. I'm not really used to the college system and the whole taking notes thing. Especially for a math based science like Chem. I feel like words aren't that important. So I...

[b]1. Homework Statement [ Average speed of helium at 25C is 1255m/s. Convert this speed to mph Homework Equations The Attempt at a Solution umm i tried to use this: 1255m/s (1mph/.477 m/s) thats all i have and i don;t know if I did this correct

Homework Statement Calculate the molar percent of nitrogen in 1kg of Ni(NO2)2. Homework Equations mol% of A = n(A) / n(total) * 100 The Attempt at a Solution I'm stuck on this basic question. I have a tendency to say that the molar percent of nitrogen would basically be...

i need to perform a demonstration/experiment that relates to chemical equilibrium for my class, does anyone have any ideas? the materials have to be found in a high school class room the experiment should be fun and not dangerous

Question: A 25 mL sample of H2C204 solution required 19.62 mL of 0.341 M NaOH for neutralization. Calculate the molarity of the acid? The reaction was : H2C204 + 2NaOH ---------------------> Na2C2O4 + 2H2O Attempt: [Which line has the mistake in it and what is it?] converted 25mL to L...