Concentration Definition and 583 Threads

Suppose i have a spherical volume of 100nm with a solution 30mM. How many solute molecules it corresponds to? My answer is about 6400...is that correct? im just not sure i did some conversion correctly... Thanks Alfio

Hello everyone, This a question related to ATP pump that uses electrochemical gradient to provide energy to make ATP. I have few questions about this. 1. In an electrochemical gradient there are more positively charged ions on one side of the membrane(In proton gradient case). So why do...

Question: A voltaic cell is constructed with two silver-silver chloride electrodes, each of which is based on the following half-reaction: AgCl(s) + e- = Ag(s) + Cl-(aq). The two cell compartments have [Cl-]= 1.41×10−2 M and [Cl-]= 2.70 M, respectively. What is the emf of the cell for the...

What exactly is the difference between a concentration cell and galvanic/voltaic cell? How do you know what are the half reactions? Also, is the ion and electron flow the same found in voltaic cells or is it the opposite? My biggest question of electrolysis has to do with Cl species...

Hope you can give me a hand here guys. I'm finding the whole carrier concentration thing a bit confusing! Si doped with say 10^17 P (/cm3). At 300K, calculate n, p, E_F (Fermi energy). Now I know the relations such as n=(N_c)exp[(E_c-E_F)/kT], N_c given I just can't figure out...

Homework Statement You have a solar cell with a constant electron density n, and known dimensions. I am looking for the change in density due to diffusion, so basically the diffusion current. All other relevant parameters are also known (temperature, D diffusion constant, etc.) To summarize...

Huge concentration of energy! 1.It's told that before the big bang everything was comressed in a very small space (as small as an atom, some say as small as a coin). My point is even if matter was not created at that time, there should be some limit to the concentration of energy (or...

Tomorrow I have an exam and my teacher gave us a hint to understand why the concentration to volume curve looks like the formula x2 but I can't find it anywhere's can someone take a quick second to explain. C = mol/L

I have been trying to find the concentration of copper in a copper sulphate solution and i was wondering if someone could check my calculations and maybe set me straight on a few things. Rep will be given of course. Titration I put 25cm^3 of copper sulphate solution into a conical flask, and...

I'm trying to find PhD programs in math that offer number theory as a focus. Where do I find this sort of information besides looking at each individual school? Is there some sort of catalogue or list that readily offers this information?

Homework Statement A sample of air was collected to assess the safety level of nitrogen trichloride in the air around a swimming pool. It was found that the air contained 0.0025% by mass of nitrogen trichloride. Calculate the molar concentration of nitrogen trichloride in the sample collected...

I am really confused about how to approach the following question. Can someone please help me out? A buffer is made by mixing CH3COO- and CH3COOH of the same concentration of 0.5M. If the volume of the former is v1 and the latter is v2, show algebraically that the following will always hold...

How do you get from a concentration to an effective dose? For example, if you have 10-9 Ci/cm3 of tritium in a human body, then how do you get the effective dose to that body? Thanks

There is a tank that contains 10,000 gallons of a weak salt solution. The salt concentration is 1300 parts per million. Now we start adding 130 gallons per minute of water and also remove 130 gallons per minute of salt solution. Thererore the salt solution concentration gradually decreases to...

Solution A: is a dilute soultion of potassium iodate, KIO3 which is the source of iodate, IO2(1-) Solution B: contains some starch and the other reacting species, the hydrogen sulfite ion, HSO3(1-) 1. In a small beaker obtain about 50mL of solution A (0.02 M IO3(-)) and in another small...

Homework Statement I'm doing my best to figure out how these answers were worked out. We discussed it as a class but then moved on to another topic and after that, I just lost it because of the topic I'm doing right now. I basically need to explain how these answers can be worked out...

Homework Statement what is the weight percent concentration of SO2 in the exsolved aqueous fluid phase that existed with solution if sulphur has ppm by weight of 90. partition coefficient= 47 Homework Equations partition coefficient- 47= concentration of aqueous fluid/ concentration of...

In what general way could I go about finding out M of Ca 2+ given a standard calcium carbonate solution and after the addition of 3 X 10 ^ -4 M of sodium carbonate at 25 degrees Celsius. I haven't done chemistry in years and would appreciate any help getting started.

Homework Statement How many grams of NaCl (molecular weight=58.5g mole^-1) would you dissolve in water to make a 0.5M NaCl solution with 500mL final volume? Homework Equations The Attempt at a SolutionSince, 1 L of 58.5g NaCl is equal 1M I used this to firstly convert 500ml into...

Hello everyone. Just a quick question: Could somebody explain to me what atomic concentration is, and whether there is a list of all the atomic concentration of the elements somewhere in the internet. The 1st time I heard the term, I typed it on wikipedia and google, surprisingly the...

Hello, I have a rod of two different diameters and I'm trying to find the stress concentration at the chamfer between the two diameters. I understand how to find the stress concentration factor, K, if the joint was a fillet (using r/d and D/d to find K in the appropriate table). However I can't...

Upon some calculation I arrive to the expression: d2DPn(x)/dx2 = DPn(x)/Lh2 Where: DPn(x) = Pn(x) + Pno - excess minority carriers (holes) concentration in the n-type part of the pn junction. Now the roots to the characteristic equation are +/- 1/Lh where Lh is the length of the...

I'm currently finishing up my third semester in Civil Engineering. Recently a couple of my friends switched from standard "Civil Engineering" to "Civil Engineering with Concentration in Management" So this got me thinking if I should switch.. If i switch, I would not be taking...

This may not even be a valid question, as I may have misunderstood; but here goes... At 25C, the KW of water is 1 x 10-14 If you increase the amount of hydogen ions present, why does the concentration of hydroxyl ions present alter in such a way that the KW is maintained (i.e. the product of...

Ok hydrogen ion gradient drives ATP synthase. In secondary active transport the preexisting concentration gradient drives the molecules. My question is what do they mean when they say concentration gradient provides energy to do this. Is it the movement of ions like hyrdogen from high to low...

How does one calculate the intrinsic carrier concentration Ni for silicon as a function of temperature? I know the equation ni^2 = Nc*Nv exp(-Eg/kT) can be used, but then another equation is needed to find the energy band gap Eg. The effective density of states values Nc and Nv are well...

Homework Statement Is there any way to calculate a solution's concentration (mass percentage - that is, the percentage of the solute mass to the solution mass) just by knowing its index of refraction? If it helps, the solute is NaCl, so I know the molar mass of the solute. I also have the...

Homework Statement Show that concentration of a substance obeys the diffusion equation if the rate at which substance leaves a region is proportional to the concentration gradient. Homework Equations Diffusion equation: \nabla2\phi = (1/a) (d(phi)/dt) where Phi is a function of r, t...

Homework Statement In a sample of GaAS at T=200k, we have experimentally determined that n0=5p0 and that Na=0. Calculate n0,p0, and Nd. Homework Equations The Attempt at a Solution Have solved that ni for GaAS at 200k is 1.2687cm-3. And using the mass action law equation...

Homework Statement Consider the reaction with the rate law, Rate = k[BrO3-][Br-][H+]2 By what factor does the rate change if the concentration of H+ is decreased by a factor of 3? Just put in the number as a whole number or fraction. Homework Equations The Attempt at a Solution...

Hello all, I am trying to revise over acids and bases before my exams, but there is one question I am stuck on, and I am not sure how to approach it. Any hints would be great ^^ "100mL of HCL of pH of 4.0 is mixed with 100mL of HCL of PH of 5.0. Whats the resulting pH of the solution...

Homework Statement trying to work out the answer for the temperature T from the equation... (1012)2=(2.8*1019)(1.04*1019)(T/300)3exp(-1.12/KT) Homework Equations the equation was derived from ni2=NcNv(T/300)3exp(-Eg/KT) The Attempt at a Solution Only simplified the equation to...

A tank contains 4000L of pure water. Brine that contains 30g of salt per liter of water is pumped into the tank at a rate of 25L/min. Show that the concentration of salt after t minutes (in grams per liter) is C(t) = 30t/160+t What happens to the concentration as t --> infinity lim C(t)=...

I have recorded cross sections of a surface layer on a substrate in a scanning electron microscope (SEM), and took EDX (energy dispersive x-ray spectroscopy) linescans across the layer. These are typically given in counts or cts per second. Now, I know the average thickness of the layer...

We know that Vmax depends on enzyme concentration since Vmax = k2[E] However, what I have trouble grasp is that why Km does not depend on enzyme concentration if Km is the substrate concentration where V = 1/2 Vmax. If you increase Vmax, shouldn't Km increase as well since it is dependent on...

iron(ii) can be determined by redox titration with a cerium (iv) solution. the oxidation reduced reaction is fe2+ + ce2+ = fe3+ + ce3+ what is the concentration of fe2+ if it requires 21.35mL of .3136 ce4+ to titrate a 10.00mL aliquot to the endpoint.

the question is at below. 320ml of 29wt% of ammonium hydroxide 1210ml of 31wt% of hydrogen peroxide 30190ml of water mixed together. What is the concentration of ammonium hydroxide and hydrogen peroxide now? Is there any reaction occurs between them?

Hi, I've been pondering over the properties of a beam of light and I'm curious if the concentration of photons in eg. a laser beam can be calculated. To elaborate on this question, let me ask if we can calculate the number of photons in a beam of light x distance long with a given cross...

Hello!.. I would like to ask something. How should I calculate the concentration of a solution?or how to set (by the use of calculation) concentration of a solution. We are about to start our research and we are assigned to set up concentration of a solution but we don't know to do it. We...

Homework Statement Calculate the concentration of Hg+2 at equilibrium in a solution that is initially 0.10M in Hg+2 and 0.50M in CN-. K instab for [Hg(CN)4]2- = 3.0 x 10 -42 Homework Equations K instab The Attempt at a Solution [Hg(CN)4]2- --> Hg2+ + 4 CN- Initial Conc...

Hi all: I'm working in a air pollutant level sensing system, to measure the common air pollutants and their level. I begun with this some months ago (In fact I've taken the others work's in my hands), and used electrochemical gas sensors for low ppm sensing (Up to 50ppm) and with 0.1ppm...

Hi, I am trying to test the validity of a simple lithium ion battery model that I consctructed to better understand the internal stress caused by the diffusion. I have referenced several papers and I am currently looking at how to calclualte the partial molar volume for a given material. To...

Homework Statement Calculate the [H3O+] concentration (in M) in a 0.1 M aqueous solution of NH3. [Kb = 1.8 x 10–5 ] (a) 7.5 x 10–12 M (c) 1.8 x 10–6 M (b) 3.0 x 10–10 M (d) 1.3 x 10–3 M Homework Equations ΔTb = Kb x m The Attempt at a Solution So... I'm kind of at a loss here...

Homework Statement calculate the formate ion concentration and pH of a solution that is 0.05m in formic acid (HCOOH;Ka=1.8x10^-4) and 0.10M in HNO3. hey guys just wondering how the equation goes?? like this?? HCOOH + HNO3>>?

Should I take a concentration with my physics major? What are the benefits? I'm interested in astrophysics, should I take a materials science or astronomy concentration?

sorry i already made a similar topic before but i didnt get any response so i decided to be more specific. i am an applied physics major freshman. i have to pick a concentration of studies but i don't know what to pick. what are some possible career paths for dual majoring in applied...

A "concentration" degree vs a "regular" degree Good afternoon everyone. I'm new here and it's great to be here. I have a very large interest in Physics and plan on getting a degree in said field. I do have one big question; Is there a big difference between having a BS in Physics and a BS in...

Homework Statement Calculate the molarity and mole fraction of acetone in a 1.00 m solution of acetone, CH3COCH3 (d=0.788 g/mL) in ethanol, C2H5OH (d=0.789 g/mL). Assume that the volumes of acetone and ethanol add. Homework Equations The Attempt at a Solution I'm not sure if I'm...

Homework Statement In this experiment you will find the ionization constant for ammonia, a weak base. I have completed the experiment, and have the following: Initial concentration of NH3: 3.708mol/L Initial pH of NH3: 10.26 Homework Equations NH3(aq) + H2O(l) <--> NH4+(aq) +...

1. COCl2(g) D CO(g) + Cl2(g) Kp = 6.8 x 10-9 at 100oC What will be the equilibrium concentrations of all 3 gases if 1.0 atm of phosgene (COCl2) is placed into 5.0L reaction vessel? The answer is [COCl2]eq = 0.033M [CO]eq = [Cl2]eq = 2.69 x 10-10M I don't get how the second one...