What is Concentration: Definition and 583 Discussions

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. R

    How to Combine Stress Concentrations for Multiple Keyways on a Shaft?

    Hello I have done a Soderberg shaft design calculation, taking into account the stress concentration for a keyway. However, I've just noticed that I might need to adapt this for a feather type keyseat, or 2 (parallel, 180deg apart) keyways in the same cross section. I'm sure I read...
  2. R

    Ka, Kb, calculating concentration of F-

    Homework Statement Calculating concentration of F- for .158M of HF? Calculate the equilibrium concentration of F- for .158M of HF in the reaction below.? HF+H20=H30+F- The Kb is 6.66*10-4 Homework Equations Kw=Ka*Kb Ka=[H+][A-]/[HA] The Attempt at a Solution I figured...
  3. P

    Finding ion concentration after determining whether precipitates will form

    Homework Statement A. Show by calculation whether a precipitate will form when 50.0ml of 0.010M AgNO3 is added to 50ml of 0.0010M Na2CO3. B. What is the carbonate ion concentration after equilibrium is established in the previous question? Homework Equations What I'm working with is: Ksp of...
  4. H

    Equilibrium fermi level and carrier concentration

    Problem statement: Determine electron and hole concentrations in Si at room temperature given that the Fermi level is 0.20eV above the valence band energy. So my thoughts on this problem: First we draw the band diagram, and it's clear that this is P type. Then, p0 = Nv * exp((Ef - Ev)/KT)...
  5. C

    Re-arrangement of Stress Concentration Calculation

    Hi i was wondering if anyone could help me by showing me how to re-arrange this equation: a=2b*(c\d)½ i need to make c the formula. Any help would be greatly appreciated. Chris
  6. Topher925

    Electrochemical cells: Is gibbs free energy dependent upon concentration?

    Is the gibbs free energy of some reaction in an electrochemical cell dependent upon reactant concentration? The Nernst equation clearly states that open circuit potential is dependent upon concentration, and basic thermodynamics states that open circuit potential is directly proportional to...
  7. J

    Concentration of minority carriers in a pn junction

    Homework Statement A semiconductor p-n junction is fabricated where the doping concentration on the p and n sides of the junction is Na=1E18cm^-3 and Nd=1E16cm^-3 respectively. Given that ni=1.18E10cm^-3, T=300k calculate: a) The majority and minority carrier concentrations in the...
  8. W

    Should I do my MechE concentration in nuclear power or in something else?

    I had been planning for awhile to study nuclear engineering at the undergraduate level and eventually do graduate work and enter the field. Now, with what happened recently, I mean is the field shot? I really find this stuff interesting and am wondering if the field still has a good future...
  9. W

    Solving Drain Problem: Salt Concentration in Effluent

    drain problem? Homework Statement A tank has 1000 m3 of salt solution. The salt concentration is 10 kg/m3. At time zero, salt-free water starts to flow into the tank at a rate of 10 m3/min. Simultaneously salt solution flows out of the tank at 10 m3/min, so that the volume of the solution...
  10. T

    Stoichiometry to find the concentration of O2?

    2 Mn2+ + O2 + 4 OH- -> 2 MnO2 + 2 H2O ***** Use the stoichiometry of the chemical reaction to calculate the concentration (mg/L) of O2(aq) and concentration of O2 (aq) (Molarity). DI Water (22 degrees C) Initial Buret Reading: 20.0ml Final Buret Reading: 28.7 ml Volume Na2S2O8 to reach the...
  11. M

    Calculating Chloride Ion Molar Concentration

    Homework Statement What is the molar concentration of chloride ions in a solution prepared by mixing 100 ml of 2.0 M KCl with 50 ml of a 1.5 M CaCl2 solution...? I don't know where to start... Homework Equations The Attempt at a Solution
  12. T

    Solving the Concentration Gradient: A Calculation Challenge

    I have a problem with calculating the concentration gradiant. Here is the question and the solution from the solution manual and the numbers don't add up. A 1-mm sheet of FCC iron is used to contain nitrogen in a heat exchanger at 1200℃. The concentration of N at one surface is 0.04 atomic...
  13. B

    Solving Doping Concentration: Temperature for 10% Hole Concentration

    Homework Statement Silicon is doped with 10^16 phosphorus atoms/cm^3. At what temperature would the hole concentration be equal to 10% of the ionized impurity concentration? 2. Homework Equations I am very confused with the equation I have . The translation of the question is I...
  14. C

    Moles...Moles"Calculate Salt & Water Concentration: 3L & 250g NaCl

    Homework Statement Calculate the concentration of water and table salt, when 250 grams of table salt NaCl is in 3 litres of liquid. Table salt has a molecular mass of 58,5 g/mol. Homework Equations Give the answer in two decimal precision The Attempt at a Solution What do they mean...
  15. E

    Solving an Ansys WB Stress Concentration Issue on Stiffener Tip

    Ansys WB, getting non-realistic stress conce. (stiffener tip on pipe column face)?? Hi, I am facing a problem in getting accurate stress in Ansys WB for stiffened base plate supporting pipe column (See attached pics) The problem is that I'm getting very high stress concentration at the tip...
  16. L

    Finding concentration of Permanganate

    Homework Statement Calculate the KMnO4 concentration of the solution in the cuvet. The Solution in the covet was made by mixing 5.00 ml of 1.00 M H2SO4 and 1.00 ml of the stock 2.00x10-3 M KMnO4. Homework Equations m1v1=m2v2The Attempt at a Solution I've tried using the dilution formula...
  17. K

    Calculating Molality of a Sulfuric Acid Solution

    Homework Statement You are given a 77.0% solution of sulfuric acid, H2SO4. What is the molality of this solution? The density of the H2SO4 solution is 1.303 g/mL. Homework Equations The Attempt at a Solution I know I divide 77.0 by 100, and then I have no idea from there.
  18. M

    Semiconductor Carrier Concentration Basics

    I have been told that the relationship n.p = (n_i)^2 always holds, where n_i is the intrinsic carrier concentration. This makes sense to me for an un doped semiconductor (sc.). However, for a doped sc., I'm a tad confused. For an n-doped material say, the electron conc. is...
  19. K

    Calculating Maximum Silver Plating from AgNO3 Solution

    Homework Statement Silver nitrate solutions are often used to plate silver onto other metals. What is the maximum amount of silver (in grams) that can be plated out of 4.6 L of an AgNO3 solution containing 3.7% Ag by mass? Assume that the density of the solution is 1.01g/mL . Homework...
  20. B

    How do you calculate carrier concentration in a doped semiconductor?

    I have a homework on Solid state device the question is :"If a Si sample is doped with 10^14 boron atoms per cm3 then determine the carrier concentration in the Si sample at 300K."[/b] I thought that the concentration is calculate by n = 2[(2pi*un*kT/h^2)]^(3/2) is this right formula ...
  21. MysticDude

    Chemistry Concentration of Molecules in the Air

    Homework Statement At a height of 300km above the Earth's surface, an astronaut finds that the atmospheric pressure is about 10-8 mmHg and the temperature 500 K. How many molecules are there per milliliter at this altitude? Homework Equations The Attempt at a Solution I first...
  22. S

    Chemistry How do you work out the volume and concentration when moles are given?

    Hi everyone. I was doing a past paper. I got some of the question wrong about finding out Volumes and Concentrations Could you please Help me with these Question. I have enclosed the question sheet that has all the work done on it. If you can't see image properly then use this link...
  23. C

    What are the concentrations of HA and A- at this point in concentration?

    Homework Statement 0.00116 moles of a weak monoprotic acid was dissolved in 25.0 mL in water. This solution was titrated with 10.0 mL of 0.0633 M NaOH. What are the concentrations of HA and A- at this point in concentration? Homework Equations The Attempt at a Solution
  24. E

    Simple Diff EQ - Modeling the salt concentration of a pond

    Homework Statement The problem can be found here: http://alex.fangsoft.net/math.pdf I have completed Task #2, it is Task #1 that I am very lost on. Our teacher has really thrown us head first into the water with this one, I am very unfamiliar with differential equations and their...
  25. M

    Concentration of Ca 2+ and Mg 2+ from EDTA titration?

    Homework Statement This is the lab I did: http://chemistry.depaul.edu/wwolbach/205_207/11.pdf only steps 1,2, & 3 was performed Homework Equations MV1=MV2The Attempt at a Solution I need help finding the concentration of Ca 2+ and Mg 2+. I already know the basics of it, but I really don't...
  26. K

    Diffusion, molecules will flow from high concentration to low

    This might be a stupid question, but it has me kind of confused. In diffusion, molecules will flow from high concentration to low concentration, and the explanation typically given is that in the laws of thermodynamics there is a net increase in entropy over time. But I am trying to think of...
  27. W

    Relationship between cell potential and concentration

    I did a lab using an electrochemical cell to establish a relationship between cell potential and concentration. I derived two equations from lines of best fit. One is Cell potential of Ag vs. Cu Concentration: y = -0.04520x+0.5515. The other is cell potential of Zn vs. Cu concentration: y =...
  28. C

    Engineering guidance (rethinking concentration)

    Hey guys, looking for some advice from some more experienced engineers and students. I'm currently a junior in the Mechanical Engineering program at my university, but I've recently begun to think that this may have been the wrong choice. I don't know if this is how it is in other programs...
  29. M

    Question about necessary concentration of urea for radish growth

    I have a project in my grade 11 biology class to design a controlled experiment showing how some factor affects plant growth, specifically radishes. I have decided to add urea as a nitrogen fertilizer to one group and do nothing to the other leaving all other factors the same between the two...
  30. J

    How to Calculate [HT-] in a Saturated Solution Using Titration Data?

    Homework Statement show the calculation for [HT-] in your saturated solution for part 2. titration- 14.30ml 0.04M sodium hydroxide i used. 2.005g KHT and 8.5g NaNO3 i diluted the NaNO3 to 100ml and added 2g KHT. filtered it then titrated with sodium hydroxide. Homework Equations...
  31. F

    Calculating concentration of diluted solution by titration

    Homework Statement Hi, I'm a bit confused with which volume to use when calculating the concentration of a diluted solution. In my problem, we're given an unknown concentration of H2O2 to titrate with a given concentration of KMnO4 solution. I have calculated the number of moles of H2SO4 in...
  32. I

    How To calculate molar concentration?

    A 40 ml volume of iron nitrate (1.8M) is mixed with 21.5ml of iron nitrate (0.808M) calculate the molar concentration of the final solution. what would be the steps to solve this problem. I am assuming i have to find the number of moles of each given the data but from there I am unsure.
  33. T

    Calculate the molar concentration of substrate

    Homework Statement Hello, I'm creating a Michealis/Menten curve and need to find the X values for the graph. Homework Equations These are the instructions given to find the X values: To obtain the X value, plot the molar concentration (molarity) of substrate used in each well...
  34. J

    Calculating Molar Concentration for Beers Law Plot

    hello everyone, i need to do a beers law plot. i got the percent transmittance which i converted to absorbance but I am not sure how to get the molar concentration. i found the max wavelength to be 515 nm. I prepared three 8-10ml diluted solutions by mixing a standard solution x (0.100M) and...
  35. F

    Chemistry Finding the Moles and Concentration

    Homework Statement Hello, 1. I just have a simple question to ask and I just want to confirm my answer. The teacher gave us a solution of NaHSO3. The data given with is were 12.0g/2.0 L. When finding the mole of the solution: n=12.0g /104.06191 or is it 6.0g/104.06191 because of the two...
  36. A

    Concentration of an original solution

    Homework Statement When 38 mL of 0.1250 M H2SO4 (sulfuric acid) is added to 100 mL of solution of PbI2 (Lead(II) Iodide) a precipitate of PbSO4 forms. The PbSO4 (Lead(II) Sulfate) is then filtered from the solution, dried, and weighed. If the recovered PbSO4 is found to have a mass of 0.0471...
  37. A

    Calculate Selenium Conc. in Phoenix Tap Water (mg/L)

    Homework Statement Suppose the concentration of phosphate in Phoenix tap water is 7.3 ppm (mass based), then what is the concentration of selenium in milligrams per liter? The density of water is 1 g/mL. Homework Equations Phosphate: PO4-3; 7.3 parts/million The Attempt at a Solution...
  38. Z

    What actually happens to concentration of species at neutral point of

    What actually happens to concentration of species at neutral point of an indicator (say that of a weak acid)? HIn----> H+ + In- (In=indicator)
  39. Z

    Concentration of solids and liquids in Chemical Equilibrium

    Homework Statement Why don't we take into consideration the concentration of pure solids and pure liquids in equilibrium constant expression? I read that their concentration per unit volume does not change. If the concentrations (moles per litre) don't change then it won't undergo any...
  40. T

    Calculating Required Volume for 1M HNO3 Solution: Nitric Acid Concentration

    Homework Statement Nitric acid is commercially available as a 72% ( w/ w) solution ( density, 1.42 g/cm3). How many milliliters of this reagent are needed to prepare 2.00 L of a 1.00M HNO3 solution? Homework Equations C%= (g HNO3/ g Solution) * 100 The Attempt at a Solution So...
  41. C

    Calculating the concentration of radon?

    Hello people, I'm needing help in calculating data or treating the data. I get measures of counts vs channel, using a silicon detector for detecting radon progeny. These peaks are Po218 and Po214, now how obtain or how understand... obtaining the concentration of radon...
  42. L

    Why convection happens when concentration gradients exist?

    Hello, everyone! I could not imagine what force makes this convection under concentration gradients , no matter how hard I thought. Maybe we can use principle of entropy increase to explain it, but that is not vivid to me. anyone can help me? Thans!
  43. U

    What is the concentration of bromide present in a 0.659 M. solution of CaBr2

    Homework Statement The arsenic in a 1.42 g sample of pesticide was converted to AsO43- by suitable chemical treatment. It was then titrated using Ag+ to form Ag3AsO4 as a precipitate. If it took 33.7 mL of 0.113 M Ag+ to reach the equivalence point in this titration, what is the mass...
  44. P

    Dynamical Concentration Equation for Water Tank System with Flow and Cleansing

    hope someone can help me to find a mathematical decription for the following problem: - there is a system (water tank) with a volume Vs in which a substance is dissolved with the concentraiton Cs - volume is drained out of the tank with a flow Vo' ("o" for out) - the volume is cleansed...
  45. J

    Analysis necessary to reduce the concentration of PCBs

    Hello i have a problem with my homework and i hope someone can help me? because i really don't know how to calculate this so its translated with google translate :blushing: Major customer PCB (polychlorinated biphenyls, a hazardous substance used in manufacture of transformers and...
  46. M

    Calibration curve and concentration?

    calibration curve and concentration?? The following is all of the data I have from a AAS/FES for water analysis. I need to make the calibration curves for calcium and sodium. and then I have to find the concentration. can someone please help me with this? i know that the Abs values will be one...
  47. D

    Finding mixture concentration using Beer's Law

    Homework Statement A 0.0450 M solution of para-aminobenzoic acid had an absorbance of 0.844 at 267 nm in a 1.00 cm cuvet, and an absorbance of 0.034 at 240 nm. A 0.0366 M solution of nicotinic acid had absorbances of 0.010 and 0.755 at 267 and 240 nm, respectively. A MIXTURE of PABA and...
  48. T

    Concentration of [H+] ions in a solution

    Hey guys, just a quick question: If you have a solution of nitric acid, and if you were asked to find the concentration of H+ ions in the solution, would you find the concentration of H+ ions in the acid plus in the water? Re-wording of question: you find the moles of H+ ions in acid +...
  49. T

    Concentration of ions in a reaction

    Alright guys, I am a little bit confused on how to find the concentration of ions in a reaction. In a solution, it is relatively easy. Are the number of ions in the beginning the same they are in the end? Please give me some general guidelines: i know to begin with a balanced equation ...
  50. G

    Finding change in concentration over change in time

    Homework Statement At a certain temperature, the reaction 2NO2(g) --> 2NO(g) + O2(g) progresses in a 4.00 liter vessel at a rate of 0.88 mol · L−1· s−1. What is \Delta[NO2] \Deltat under these conditions? Answer in units of mol · L−1· s−1. Homework Equations C = n/v ...
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