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. Y

    Concentration and diffusion of oxygen in the Earth's atmosphere

    Homework Statement 1. Estimate the concentration of oxygen in the Earth's atmosphere (in molecules / m^3), at room temperature and at sea-level, assuming the fact that oxygen comprises 21 percent of the Earth's atmosphere by volume. 2. If you were to place a perfect oxygen sensor of...
  2. N

    Finding Concentration of a Standard Solution using % purity ?

    Homework Statement I need to know the concentration in ppm of a standard Fe2+ solution. (diluted) Here is the data I have. I have 0.1964 g of Fe solution the purity is 99.7% The original solution was the above # of g in 250ml water. 10ml of this was then pipetted into a 100ml volumetric flask...
  3. E

    Calculating Acetic Acid Concentration: Henderson Hasselback

    Homework Statement What is the concentration of acetic acid in 250mL of a 100mM acetate buffer at pH 4.76? Homework Equations Henderson Hasselback The Attempt at a Solution I used the Henderson Hasselback equation. plugged in 4.76 for pKa. plugged in .025 for the concentration of...
  4. C

    SA + SB always give pH= 7 even if concentration of SA is a lot bigger than SB?

    SA + SB always give pH= 7 even if concentration of SA is a lot bigger than SB? let's say 10 M of HCl react with 0.1 M of NaOH, is the pH at equivalence point also 7?
  5. S

    Finding concentration of an incoming solution

    Homework Statement A tank holds 10 L of pure water. Brine (unknown constant concentration) is flowing into the tank at 1 L/min. The water is mixed well and drained at 1 L/min. After 20 min, there are 15 g of salt left in the tank. What is the concentration of the salt in the incoming brine...
  6. L

    Maximum stress and stress concentration factor (SCF)

    Hi guys, have been struggling with this exercise, could anyone give any help? thank you so much!
  7. D

    Integrating a concentration profile

    Hello- I have a diffusion profile, in which I plot the decrease in concentration versus distance of my sample. I am trying to find the increase in mass of the overall sample. How would I do this? I have integrated the function and am wondering what type of information that would supply...
  8. L

    Does Change in NaCl Concentration Indicate Ion Quantity?

    Homework Statement For instance I have NaCl. I found a relationship between conductivity of NaCl in water and concentration of NaCl in the water. It's; conductivity is approx 0.5 concentration Is it correct that the change in concentration gives the number of ions? For example say I...
  9. H

    Chemistry: Using Formation Constant to calculate an end concentration

    Homework Statement 50.0 mL sample of 2.0 10–4 M CuNO3 is added to 50.0 mL of 4.0 M NaCN. The formation constant of the complex ion Cu(CN)3 is 1.0 10^9. What is the copper(I) ion concentration in this system at equilibrium? The Attempt at a Solution I did a dilution and got the new...
  10. D

    Measurement of concentration of urea

    Dear All Does anyone have any idea about how to determine the concentration of liquid urea. The concentration is a bit higher (0.5-1.5 mol/L). Is there any laboratory techniques or Kit? I looked for and found everywhere the method to measure the amount of urea in blood and urea but what I want...
  11. R

    Concentration problem using absorbance

    Homework Statement Hi. A patient produced 1122 mL of urine in 24 hours. A 1.00-mL aliquot of the sample was treated with Mo(Vl) and ascorbic acid and was diluted to a volume of 50.00 mL. A calibration curve was pre- pared by treating 1.00-mL aliquots of phosphate standard solutions...
  12. C

    Calculating Light Source Power from Photon Concentration & Wavelength

    Hello all of you very bright physicists, The local physics dept. is not answering us thus far and long story short we need a rough estimate of the power of a light source based on wavelength and a measured concentration of photons. We need a method of converting the photon concentration...
  13. schrodingerscat11

    Getting the concentration from Scanning Electron Microscope

    Greetings! I am doing particle analysis using a JEOL 5310 Scanning Electron Microscope (SEM). Typically, people here in the lab report the results in % Element or % Atomic. I think the former refers to the weight percentage of an element and the latter to the stoichiometric ratio of...
  14. M

    Calculating the Ka from pH and initial concentration

    Homework Statement A 0.0200 mol/L acid solution has a pH of 2.347. Calculate the percent ionization of this acid. Calculate the Ka of this acid The Attempt at a Solution I first calculated the hydronium ion concentration: 10^-pH = 10^-2.347 = 4.5*10^-3 I then used this concentration...
  15. A

    Calculate Volume for 0.1M HCl Solution in 300ml at 32%

    What is the volume you need to take from 32% HCl solution in order to get a solution in final volume of 300 ml and with Molar concentration of 0.1 M. The solution density is 1.159 gr/ml. I don't understand why will we have change... the mass will stay the same won't it? and the density is...
  16. J

    What is the Correct Concentration of Sr2+ in a Saturated SrSO4 Solution?

    Homework Statement A saturated solution of SrSO4 has a [SO42-] of 1.0x10-4M. What is the [Sr2+]? A. 3.4x10-3M B. 5.8x10-4M C. 1.0x10-4M D. 3.4x10-7M Homework Equations The Attempt at a Solution It's a multiple choice practice test and the answer key tells me that A is the...
  17. S

    Semiconductor Physics : Charge carrier concentration change on doping

    Hi, I have a question regarding the change in charge carrier concentration change. For a given semiconductor, say Silicon, when it is not doped, it is easy to understand that {n_0} \times {p_0} = n_i^2, however, on doping with donors to form a n-type semiconductor, we have {n_0} \approx...
  18. X

    Chemistry Calculating the Concentration of N/5 HCl After Removal of 3.65g

    Homework Statement On boiling 1litre of N/5 HCl, the volume of the aqueous solution decreases to 250ml. If 3.65g of HCl is removed from solution, then the concentration of resulting solution becomes? N/5 N/2.5 N/20 N/10 Homework Equations HCl=36.5g/ mol The Attempt at a Solution...
  19. O

    Chemistry Calculate Reactant Concentration from Chemical Equilibrium Moles

    If someone could check my work on this, I'd appreciate it: Thanks!
  20. C

    What is the concentration of chromate?

    What is the concentration of chromate?? Homework Statement A solution of K2CrO4 has an absorbance value 0.555 in a cell of 1.00cm path-length at a wavelength of 370nm. The value of the molar absorbtivity is 5.25x103M-1cm-1 for K2CrO4 at the wavelength. What is the concentration of this...
  21. J

    PH, Alkalinity, and total carbonate concentration

    Homework Statement If the pH of a natural water is 7.8 and the alkalinity was measured to be 125 meq/L, determine the following: -Alkalinity as mg/L CaCO3: Answer = 6250 mg/l CaCO3 -Approximate the total carbonate concentration CT, in moles per liter: Answer = 0.125 moles per liter...
  22. P

    AP CHem, finding concentration of H2O2 by titration

    Homework Statement I need to find the concentration of the H2O2 that we usedHomework Equations 2KMnO4 + 5H2O2 + 3H2SO4 → 2MnSO4 + 5O2 + 8 H2O + K2SO4 (not sure if correct) we got an average of 34.5 ml of titrant, for solution we were adding the titrant to being 5ml of Hydrogen peroxide, and...
  23. F

    Adsorption of Benzene using Activated Carbon - Increase in concentration?

    Adsorption of Benzene using Activated Carbon - Increase in concentration!? I'm not quite sure where to post but here it goes. I'm performing an adsorption experiment of benzene from solution using commercial activated carbon. It is expected that the concentration of benzene would decrease...
  24. D

    How to calculate initial concentration

    Homework Statement A known mass of methylamine, CH3NH2, was dissolved in water at 25 celsius 50.0 cm^3 of this solution was taken and titrated with 1.00x10^-1 mol dm^-3 hydrochloric acid solution, HCL(aq). The change in pH as an increasing volume of hydrochloric acid was added is shown in the...
  25. D

    What is the Concentration of a Substance in gdm^-3 Given Volumes V1 and V2?

    Please see the attached,this is the last question of my chemistry homework but I can't figure it out.And sorry for that I can't type any attempt at a solution because I don't understand what it is asking for.And something appears in the question like V2-2(V1) confused me.Hope someone can help or...
  26. C

    Spectroscopy: Determining Phenol Concentration using Calibration curve

    Hello, My problem is as follows: The lab I am working on requires the construction of a calibration curve from the measured absorbance of samples of known phenol concentration to intrapolate the phenol concentration of two unknown samples. I have constructed the calibration curve and...
  27. D

    Half-life decomposition, find final concentration

    Homework Statement In a first order decomposition in which the rate constant is 0.03 sec-1, how much of the compound (in mol/L) is left after 39 sec, if there was 2.00 mol/L at the start? I'm using a few equations and trying to plug it in but I don't know whether they are appropriate or not...
  28. F

    Calculate the equilibrium concentration of hydrogen ions

    Homework Statement
  29. X

    Concentration of the resulting solution in this question

    Homework Statement On boiling 1litre N/5 HCl, the volume of the aqueous solution decreases to 250mL. If 3.65g of HCl is removed from the solution then the concentration of resulting solution becomes? Homework Equations No idea, from where should i start
  30. X

    What Is the Concentration of SO4²⁻ When Al³⁺ Is 0.28M?

    Homework Statement The concentration of Al3+ ion in aqueous solution of Al2(SO4)3 is 0.28M, Then the concentration of SO42- ion in this solution will be? Homework Equations Al2(SO4)3 → 2Al3+ + 3SO42- The Attempt at a Solution What should i compare to start of with?
  31. R

    Early 1900's Concentration Measurements

    I have read a few papers that were written in the early 1900's where their concentration measurements are M/4, M/8, M/16, M/32, M/256. I am not sure what this means and I was wondering if anyone could relate these concentration measurements to normal concentration measurements we use now, such...
  32. S

    Making CO2 Gas Concentrations: 50ppm, 100ppm, 1000ppm

    Hi, I have a gas cylinder 99.999% CO2. I want to apply the CO2 to my sample at different concentration. e.g.) 50ppm, 100ppm, 1000ppm. How do I make these concentrations of CO2 from my gas cylinder? Any practical advice would be truly appreciated. cheers
  33. R

    Urea sulfate synthesis (acid concentration?)

    Hi all! I am currently doing trials on different fertilizer production methods. I want to make urea sulfate crystals from fertilizer grade urea granules (46% N) and sulfuric acid. I suspect it would be a straightforward process, dissolve the urea in acid and precipitate the crystals and...
  34. N

    How Do You Calculate the Mass Concentration of N2O in Air?

    Please check if right. Determine the mass concentration for N20 at a mixing ratio of 311 ppb at P = 1 atm, T= 298 K. My work #density of N20 = Concentration of N20 * #density air PV = #moles of air R T PV/RT = # moles of air PV/RT = Numberofmolecules/Avagardo # = #moles of air...
  35. C

    Problem about charge concentration

    Hello people, I m quite new at this forum, and since I m not a native American, I may have some problems with translating the problem to English, but I will try my best. There are some problems in the same type with that in my worksheet, and I can solve none of them. Here is the question...
  36. T

    Why does diffusion always go down the concentration gradient?

    I have been wondering if there is an explanation to why diffusion always goes down the concentration gradient? If it is a random molecular movement than why do we always end up with a uniform distribution of molecules?
  37. M

    Volumetic Analysis - calculate concentration

    Please Help! Volumetic Analysis - calculate concentration Dear Physics Forum Fiends, I was wondering if anyone out there who needs to earn some extra points to get into heaven perhaps or is simply feeling extraordinarily generous, might like to give this problem a go? I am woefully lost...
  38. A

    Determining concentration of a particular substance in a solid?

    This question may sound a bit odd, but is there a relatively simple way(by simple, I mean inexpensive) to determine how much acrylamide is in a certain type of food(e.g. French fries, potato chips)?
  39. I

    K Concentration on Earth Over Time

    Homework Statement Hei!Half life of the reaction is about 1,25 billion years. Assuming that the age of Earth is 5 billion years,the concentration of K on Earth since its formation decreased: a)2times b)4times c)8 times d)16times The Attempt at a Solution So I just do like that...
  40. P

    Stoichiometry to find concentration and pH

    Homework Statement 15.1g of calcium hydroxide completely dissociates in distilled water forming 855ml of basic solution. a) Dissociation Equation b) Calculate the concentration of OH in the solution c)Calculate the pH of the above solution Homework Equations c=n/v pH=-log[H] The...
  41. M

    Concentration What you are Good at or What you find Interesting?

    Hello all, I am a Pre-Junior at Drexel University Mechanical Engineering Major. I am entering the BSMS program this fall. I need to choose a specialization for my Master's Degree. I have three choices - 1. Mechanics 2. Thermal Fluid Sciences 3. Control Systems. As my title states...
  42. Saitama

    How Much Solution Can Be Prepared with Specific Chloride Concentration?

    Homework Statement Available are 1L of 0.1M NaCl and 2L of 0.2M CaCl2 solutions. Using only these two solutions what maximum volume of a solution can be prepared having [Cl-]=0.34M exactly. Both electrolytes are strong. a)2.5L b)2.4L c)2.3L d)None Homework Equations NaCl-->Na++Cl-...
  43. Z

    How to find the concentration of nucleic acid solution using optical density?

    I just did this lab where I measured the absorbance of nucleic acid solutions and I have to find the concentration (in mg/mL) of each nucleic acid at different temperatures at 260nm. It is given that they have an absorption maximum at 260nm with an intensity of 17 OD (optical density) units/mg...
  44. schrodingerscat11

    Help: Obtaining the elemental concentration using EDX analysis

    Greetings! We are currently doing a study about the elemental composition of ambient particles in the atmosphere. Basically, here's what we do: (1) Get samples of particulates using an air sampler with known flow rate. The particulates are deposited on a filter. One filter is used per...
  45. R

    PH to Concentration of Citric Acid

    I am working on making Meads (Honey wine) and after speaking to a master Vinter he advised I lower the pH of my starting water & honey mixture to 3.5 for various reasons. I'm interested in experimenting to see if this gives a noticeable taste difference to the mead. I know honey is Basic but...
  46. M

    Calculate the mass of NaCl needed to bring sodium concentration to 0.139 M?

    A person suffering from Hypothermia has a sodium ion concentration in the blood of 0.114 M and a total blood volume of 5.1 L. What mass of sodium chloride needs to be added to the blood to bring sodium ion concentration up to 0.139 M? (assuming no change in blood volume)...
  47. I

    Volume Balance on concentration in a tank

    Homework Statement Hi. I am trying to do a volume balance on the concentration in a tank. I don't know how to find the output and just need some help. I have attached the image showing the question from the paper. Thanks. Homework Equations INPUT = OUTPUT + ACCUMULATION The Attempt...
  48. A

    Intrinsic carrier concentration formula

    In the ni=\sqrt{Nc*Nv}*e^{\frac{-Eg}{2kT}} formula for intrinsic carrier concentration, what values Nc,Nv and Eg take in relation to temperature? Are they each calculated for that temperature or, for example, is Eg always taken for 300K? My guess is they should all be calculated for given...
  49. F

    Using UV-Vis Spectroscopy to determine concentration

    I have been conducting liquid phase adsorption experiments of xylene and toluene using activated carbon. I made solutions at 2 concentrations (200ppm and 400ppm) of individual components of toluene and xylene in methanol, as a solvent. Initially, the plan was to use Gas Chromatography to...
  50. R

    Do elemental peaks on SEM-EDS spectra relate to concentration

    Hello, I recently did an experiment where I examined and analyzed crystals using SEM-EDS. One of the major parts of my experiment was to determine the concentration of a certain element (calcium) in the different crystal samples. I noticed that some calcium peaks were higher than others. Does...
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