Concentration Definition and 583 Threads

In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration. A concentration can be any kind of chemical mixture, but most frequently solutes and solvents in solutions. The molar (amount) concentration has variants such as normal concentration and osmotic concentration.

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  1. gfd43tg

    Concentration Boundary layer thickness

    Hello, I am simulating an experiment I did in the lab where we had air flow over a tray of water to determine the mass transfer coefficient scaling with velocity, as well as boundary layer thickness scaling with velocity. Now I am using COMSOL to simulate the experiment, and here is the...
  2. P

    Finding The Concentration Of An Ion

    If I have a balanced chemical reactoin, for example KOH + HBr ==> H2O + KBr And I am given the concentration and volume of both KOH and HBr, how is it possible to determine the concentration of one of the ions from the net ionic equation? H + OH ==> H2O
  3. P

    Calculate concentration of an acid

    How can I calculate the concentration of sulfuric acid with help of a neutralisation equation? (in mol/l or g/l) Neutralisation takes place with either NaOH or KOH. I've been searching for a tutorial for hours, but didn't find anything helpful. Could someone please explain me how to do it? I...
  4. gfd43tg

    Concentration boundary layer thickness

    Hello, I'm doing an experiment where I will be blowing warm air parallel to a stagnant water surface, and I will investigate the scaling of air velocity with mass transfer coefficient. I am trying to find some kind of scaling of the concentration boundary layer thickness with air velocity, and...
  5. O

    Semiconductor doping - doping concentration is 0?

    Homework Statement A sample of germaium has an acceptor concentration of Na=10^17 and a donor concentration of Nd=0. Calculate the intrinsic carrier concentration, majority carrier concentration, and Ef-Efi. Use T=400 Homework Equations No*Np=ni^2 Nv=Nv*(T/300)^3/2 Nc=Nc*(T/300)^3/2 ni^2=Nv*Nc...
  6. O

    Carrier concentration in a semiconductor

    Homework Statement The question is in the picture attached. When Na=0, that means the acceptor concentration(i.e. open holes?) is zero? Homework Equations (Nd-Na)/2 + sqrt((Nd-Na/2)^2+ni^2) (Na-Nd)/2 + sqrt((Na-Nd/2)^2+ni^2) The Attempt at a Solution Solving for Nd=10^8: majority carrier =...
  7. S

    Can I Calculate Salt Concentration in a 1500kg/m^3 Solution Using Density?

    If 50kg of salt is mixed with 100 kg of water to form a 1500kg/m^3 solution, can I find the concentration of salt by subtracting the density of water which is 1000kg/m^3, or do I have to equate it like this: 50/((50+100)/1500)=500kg/m^3 ? Is the volume of salt negligible so that the volume of...
  8. gfd43tg

    Reactor + Separator control outlet concentration

    Homework Statement Homework EquationsThe Attempt at a Solution Hello, I get confused with input and output and state variables. Since we want to control ##C_{Ao}##, I assume that needs to be the output variable in the vector ##\vec {y}##. I think the inputs should be ##C_{Ai}## and...
  9. C

    Which MSE Minor Concentration is Best for an NE Major?

    For an NE major, would a ceramics or metals emphasis be a better choice for a materials science minor? I don't start upper level NE courses until next semester, but I've already taken the prerequisite MSE intro course and want to enroll in an upper level MSE course also. I'm assuming polymers...
  10. C

    MHB Solving for A:"Solving for A: Finding Salt Concentration in Tank After 10 mins

    Hello, I need some help with part a. The problem state: "Suppose a brine containing .2 kg of salt per liter run into a tank initially filled with 500L of water and 5 kg of salt. The brine enters the tank at a rate 5 L/min. The mixture, kept uniform by stirring, is flowing out at the rate of...
  11. C

    What is the Glutaraldehyde Concentration in a 1-Liter Solution?

    1 litre solution containing 28ml of glutaradehyde and the rest distilled water. What would be the concentration of glutaradehyde in solution in mg/l please.
  12. B

    Schools Picking a concentration in grad school. .

    Hey all, I'm a math and physics graduate who will be starting math grad school in a little over a month, and, though I know I have time to decide, I'm a bit conflicted about what to concentrate in. I'm broadly interested in the applications of math in physics. Specifically, I've always had...
  13. H Smith 94

    Determining number of dissociated moles from concentration?

    Is there a formula to theoretically determine the number of moles of each ion present when a particular concentration of salt is dissociated in water? I remember from A-level (high school) chemistry that concepts such as the dissociation constant exist but I'm struggling to apply them to...
  14. A

    Diffusion, concentration profile

    I'm right now working with modelling a system, where atoms diffuse along a coordinate z until they reach a certain point z=z0 at which they are taken out of the system. The diffusion equation is: ∂n/∂t = D∂2n/∂z2 The question is now what boundary conditions to use for the concentration profile...
  15. F

    Magnetic field to increase concentration

    can I apply magnetic field to increase concentration of a gas? or I will need too big magnetic field to surpass the 1000C molecular motion?
  16. KennyJr

    Physics with concentration in Mech Engineering

    I'm almost done with my AA and was planning on continuing with my path in Mechanical Engineering, BUT the school I am planning on going to also offers Physics with a concentration on Mechanical engineering (BS). Could anyone give me an insight on this? Thank you!
  17. CupOfNoodles

    Computational Physics Concentration

    Hello, I'm new to the Physics Forums website. I am in my 5th (and last) year of undergraduate Electrical Engineering, and am planning on applying for a PhD in some computational field. I'm not sure, however, what specific field I want to go into, and I was hoping someone could give me some...
  18. G

    Quantity of matter, mass concentration, molar concentration

    Hey! I need some help please! Anyone know how I can calculate the quantity of matter, the mass concentration and the molar concentration? It is for a physics exercise! Thanks :)
  19. Carmen Wong

    Use Sauerbrey equation explain Δf Vs. analyte concentration

    1. Explain, using the Sauerbrey equation, how the change in the resonance frequency of a quartz crystal can be related to an analyte concentration 2. Sauerbrey equation: 3. I knew Quartz crystal microbalance work according to the change of frequency after mass loaded, and when working in a...
  20. U

    What is the doping and hole concentration?

    Homework Statement (a) Show law of mass action. (b) Find dopant concentration and hole concentration.[/B] Homework EquationsThe Attempt at a Solution Part(a)[/B] Bookwork. Part(b) Letting the doping concentration be ##D##, we have: D = n - p For ##I = n_{intrinsic} = p_{intrinsic}##, we...
  21. C

    Calculating Phosphate Concentration in Water: A Scientist's Perspective

    If I add 1 gram of phosphate to 20 litres of water. What would the concentration of phosphate in solution in ppm? I have somehow come up with 50ppm does this sound right? To achieve 1ppm phosphate in 20l of water I would require 0.02g? Or am a weigh off?
  22. M

    Derivation of Carrier Concentration (ni)

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > I am following a lecture on carrier concentration and I got to the point where the instructor said that for homework, derive the carrier concentration equation ni, which...
  23. R

    Pumpable slurries What concentration?

    I have an application where a slurry of salt (NaCl) in water needs to be pumped a short distance; approx. 30 ft. Flow rates are modest approx. 5000 Litres per hour. The head requirement is negligible i.e. not much of a height change other than the frictional head. What's the maximum...
  24. H

    How Does Fossil Fuel Combustion Impact Atmospheric CO2 Concentration Annually?

    Homework Statement The world burns approximately 3.8 x 1012 kg of fossil fuel per year. 1. Use the combustion of octane as the representative reaction and determine the mass of carbon dioxide (the most significant greenhouse gas) formed per year. 2. The current concentration of carbon dioxide...
  25. Kaleem Ullah

    How to Calculate Gas Concentration in a Chamber Without Sensors?

    How can we find the gas concentration in a chamber without using a sensor i mean by calculation suppose a mixture of gas ammonia 10% and CO2 90% flow to the gas chamber how we can find that concentration of gas in the chamber?
  26. R

    Refractive Index change with Wavelength & Carrier Concentration

    I need to calculate the refractive index of a semiconductor material over a wavelength range (1×10-5m - 1×10-9m) and with different values of electron and hole carrier concentrations (i.e. n/p doped). I found this equation that relates those parameters: n+ik = √ [ (εm -...
  27. B

    Is the System at Equilibrium with Given Concentrations?

    Homework Statement Consider the following reaction: H2 + I2 → 2HI (all gases) At 740 K, this reaction has an equilibrium constant of 50. If, at 740 K, the concentration of hydrogen gas is 2 M, iodine gas is 3 M, and hydrogen iodide gas is 6 M: (A) the concentration of hydrogen iodide will...
  28. Euler2718

    Solve Concentration Problem: K, Cr2O7, Equilibrium

    Homework Statement Question 9) Homework Equations K=\frac{[P]}{[R]} The Attempt at a Solution What is confusing me is the wording. It merely says for the concentration of chromate. All this time we've been doing the equilibrium concentrations. Doing mole-mole with the Cr2O7 yields the...
  29. gracy

    Why does degree of dissociation increase with decreasing concentration?

    Why degree of dissociation increases when concentration decreases?It was written in my textbook that when concentration decreases i.e on dilution there is increase in current because of increase in charge carriers i.e ions,I thought that it could be because on dilution water is added,so now...
  30. C

    Solid solution hardening, concentration dependence

    When you add impurity atoms to a material, the yield strength often increases by a process known as solid solution hardening. This is because the impurity atoms create a barrier to dislocation motion. The literature describing this phenomenon dates back to the 1960s with some famous papers by...
  31. T

    Calculating Protein Concentration w/ Bradford Assay

    Homework Statement Hi, I have one more question about the Bradford Assay. This one involves dilution. Given 1ml of protein A, I am to determine its protein concentration (in mg/ml) using Bradford Assay (with known BSA protein standards). Also, Under a 5 times dilution, the average absorbance...
  32. A

    Exploring Space-Time: Dilation & Concentration

    Hi all, I was wondering if anybody else here thinks the concept of space-time dilation/concentration (curvature) is a little bit funny, not in the sense of it having an effect on the neighbouring particles, but in the sense of actually stretching or contracting, as though it itself had certain...
  33. C

    Free electron concentration range between semiconductors and metals

    A structure with free electron density around 10^26 m^-3 is considered as a highly doped semiconductor or a metal? Or in other words, what is the lowest possible free electron concentration for a metal and what is the highest possible free electron concentration for a doped semiconductor?
  34. majormuss

    Schools Useful Computer Programming for Astrophysics concentration in Grad School

    My objective is to learn programs and techniques that will prove beneficial to my physics degree. I am going on to grad school to get a physics PhD but I will be staying 1 more year as an undergrad. A CS minor is probably too broad for me because I only want to learn specific programs that will...
  35. gfd43tg

    Feeding reactant into side to keep concentration high

    Hello, I am studying the maximizing of selectivity of a particular product with two competing reactions ##A \xrightarrow {k_{D}} D##, ##r_{D} = k_{D}C_{A}^{\alpha_{1}}## ##A \xrightarrow {k_{U}} U##, ##r_{U} = k_{U}C_{A}^{\alpha_{2}}## where D is the desirable species, and U is the undesirable...
  36. L

    100% concentration of sulfuric acid by boiling isn't possible,why?

    why can't we get 100% concentration of sulphuric acid by boiling it?
  37. L

    Equilibrium concentration question

    It has been a bit since I took chemistry, but I have been wondering something, and can't seem to remember. Let's say that I have the following: Fe3+ + SCN- <-> FeSCN2+ How can I calculate the point where Fe3+ concentrations become effectively zero? That would say, if I know that I have 1M Fe3+...
  38. juliact15

    Which courses should I take for a concentration in Astronomy?

    I am an undergraduate Physics major in my third year, and I'd like to concentrate in Astronomy or Astrophysics when I obtain my Masters and PhD. What kinds of physics classes should I take in preparation for this? I've already taken all explicitly-astronomy courses at my school. I was thinking...
  39. K

    Effusion of gas from higher to lower concentration under same pressure

    If we have a hole in a container with pressure equal to the pressure outside it and the concentration of gas inside the container is more than that outside will the gas effuse out?
  40. gfd43tg

    Concentration of species based on what basis is used

    Homework Statement For the gas phase reaction with an equimolar feed of ##N_{2}## and ##H_{2}## ## \frac {1}{2} N_{2} + \frac {3}{2} H_{2} \rightarrow NH_{3}## If you took ##N_{2}## as your basis of calculation, could 60% conversion of ##N_{2}## be achieved? Homework EquationsThe Attempt at...
  41. D

    Simple concentration problem but something's wrong

    Ok so I think I have a suitable answer to my question but because of certain circumstances I have reason to believe my answer is wrong. The question is: calculate the amount of phosphoric acid in mgH3PO4/L in a solution of concentration 2.92X10^-5 mol/L. seems pretty straight forward but...
  42. H

    Diffusion Rate and Concentration

    So the rate of diffusion is dependent upon the speed of the molecules and the existence of a concentration gradient. What about the concentration of the particles themselves? Diffusion is dependent upon mean free path and concentration is inversely proportional to mean free path. So does...
  43. M

    Finding the Concentration of Triiodide

    Homework Statement Stupid question but I'm not sure about it. In lab we added I3- and KI into a test tube and from this we have find the concentration of I3- in the final volume. The Attempt at a Solution Would the I3- be diluted by the KI that was added or does the KI end up forming...
  44. gfd43tg

    Concentration of CO in Los Angeles Basin (matlab)

    Homework Statement Smog begins to build up again immediately after a Santa Ana wind passes through the basin. The volumetric flow rate through the basin has dropped to ##1.67*10^{12} \frac{ft^3}{hr}##. Plot the concentration of carbon monoxide in the basin as a function of time for up to 72...
  45. J

    Where would the highest concentration of electrons be located?

    If someone is sitting in a typical living room? Would you care to elaborate, please and thank you!
  46. gfd43tg

    What is the significance of the change in concentration over time in a CSTR?

    Hello, Suppose A and B are continuously added into a tank, and exit stream consists of A,B,C, and D. I am a little confused on the following point as I follow the example in my textbook. The reaction is ##A + B → C + D## It says because (and I quote) ''...Because the system is operated at...
  47. gfd43tg

    Change in concentration vs. reaction rate

    Hello, I am wondering, why is it that ##\frac {d[C]}{dt} \ne k[C]## in general, where ##C## is a chemical species, and the product ##k[C]## is the reaction rate, ##r##. ##r_{c} = k[C]## My thoughts is that because the units aren't necessarily the same, therefore they can't be the same. But I...
  48. B

    Laser to determine effect of sucrose concentration on refractive index

    Hi! I want to conduct an experiment to investigate the effect of sucrose concentration on refractive index using a laser pointer however I would like to complicate this experiment as this is just a simple how x affects y experiment. It may also seem to straight forward as obviously higher...
  49. C

    Pressing fingers to nose and forehead help concentration?

    Greetings, Why does pressing one's fingers between the nose and forehead lessen distress and help concentration? Thanks
  50. S

    Concentration of paint in each bowl after certain time

    Homework Statement We are taking a closer look at three identical bowls with volume ##10l##. At the beginning only the first bowl is full with water mixed with ##0.5kg## of paint. The other two bowls are empty. Than we provide a constant flow of ##0.05 l/s## of clear water straight into the...
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