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. M

    I Dissolved gas concentration in undersaturated liquid column

    Hi, In an enclosed system - of say Methane & water - in which the water column is sufficiently large to have significant pressure and some modest temperature difference due to gravity and geothermal effects, how would one calculate / predict the changing methane concentration (or partial...
  2. I

    Intrinsic semiconductor, carrier concentration

    Homework Statement An intrinsic semiconductor with a direct gap have valance band ##\epsilon_k = E_v-b|k|^2## and conduction band ##\epsilon_k = =E_c+a|k|^2##, with ##E_v=6.0##eV, ##E_c = 5.5eV##, ##a=5.0eV\cdot Å^2##, and ##b=3.0eV\cdot Å^2##. Calculate the chemical potential ##\mu## and the...
  3. M

    Standard addition concentration positive

    I am computing limit of detection of zinc of an electrolyte. Using standard additions method, I have obtained positive x intercepts for 6/8 samples all very close to zero. Positive x-intercepts imply final concentration values to be negative. if x-intercept taken to be zero, the concentration...
  4. DavitosanX

    Increasing the concentration of a solution - Diff Eq?

    I have a question regarding a problem in chemistry. I ultimately solved it, but I wanted to know if the problem itself could be represented as a differential equation, and if the solution I found is the solution to that equation. The explanation is a little long, but I don't think I can make it...
  5. A

    Is There a Proven Way to Enhance Concentration and Improve Focus?

    Some people want to improve their powers of concentration, and even help others do the same. Perhaps some members of this forum have found useful techniques they would like to share. One thing that fascinates me is how the subconscious comes to the rescue at times. For example, I make a mistake...
  6. Farang

    Electron concentration as a function of pressure

    Homework Statement Determine electron concentration for both Helium and Nitrogen as a function of pressure at 300K. This is from preliminary task for Energy loss of alpha particles in gases laboratories. It's too late to submit this, I'd just like to understand. Can post more info from the lab...
  7. S

    Help - spiking sediment with known concentration of sulphide

    I need some assistance. I am truly missing something very fundamental. Background: I have a sodium sulphide stock solution with the conc. of 0.0429M. I prepare five standards through serial dilution (10,000; 5,000; 1,000; 500; 100uM). Buffer is added in a 1:1 with the standard - the...
  8. I

    Expressing concentrations as a percent

    You measure the concentration of O2 in seawater to be 5.0 mg O2/L H2O. Express this concentration as a percent. Question 2: The Earth's atmosphere contains 21% O2/L of air. How much more oxygen does the atmosphere hold than seawater from the previous question? So for question one I got 0.01%...
  9. N

    Shouldn't Carbon-14 concentration be the same everywhere?

    Why is it that newer organic matter has more carbon-14 than older organic matter? Isn't carbon constantly recycled, because of the carbon cycle? So C14-depleted carbon from old matter would enter the atmosphere, then be breathed in by new organic matter. The new matter would start off with...
  10. A

    Need an explanation -- Consider pure water separated from....

    Consider pure water separated from an aqueous starch solution by a semipermeable membrane, which allows water to pass freely but not starch. After some time has elapsed, the concentration of starch solution a. will have increased b. will have decreased c. will not have changed d. might have...
  11. B

    What is the [A2+] at Equilibrium When Mixed with B-?

    Homework Statement Equal Volumes of 3.60 M A2+ and 6.80 M B- are mixed. After the reaction, equilibrium is established with [B-] = 0.40 M. What is the [A2+] at equilibrium? Homework Equations Ice table, algebra The Attempt at a Solution This is probably a really easy problem, but I seem to be...
  12. A

    Molarity vs. Concentration: What's the Difference?

    Concentration measures the number of moles of solute per liter of solution, besides that it can be used to measures also the ratio of mass per liter. Molarity also measures the number of mole of a solute per liter of solution. Then what is the difference between these two definitions? They seem...
  13. Conductivity

    Sodium concentration during action potential generation

    ' At the peak of the graph, Is the concentration of Na outside the cell is more than inside? because that must be to overcome the electrical force in the opposite direction but my book says that that inside the cell there are more Na than outside When is the concentration of Na+ greatest inside...
  14. HARSHARAJ

    A Change in Fermi level with gradient of doping concentration

    In a degenerate n type semiconductor, when the doping concentration has a gradient(say -ve gradient), then how fermi energy level and intrinsic Fermi energy levels will depend upon the concentration gradient? ~If anyone knows anything about it, kindly help.
  15. A

    Making a graph of CuSO4 concentration vs volume of solution

    Homework Statement Hi, I don't even know where to begin with this type of graph. It does say that the graph should be a straight line. This is for one of my questions for my lab that I am completing. This is the link of mytable with info...
  16. G

    Programs How many concentration courses in an undergraduate degree

    Hello, I hope someone can help. I'm a high school student in Canada who is thinking about majoring in Physics in university. I've started researching different potential programs and had a question regarding the structure of undergraduate programs at US universities. How many core courses...
  17. M

    Keep losing focus when doing math

    I keep finding myself losing focus in the middle of doing even basic maths. I sometimes know exactly how something should be done, but make stupid mistakes doing it because I can't fully concentrate. I used to have an obsession with numbers (as a kid) and was great at mental maths. Now, I'm...
  18. Aafia

    Mg metal reacts with HCl to produce hydrogen gas?

    1. The problem statement, all variables and given/known Mg metal reacts with HCl to produce hydrogen gas. What is the minimum volume of HCl solution (27% by weight) required to produce 12.1 g of H2? Density of HCl solution is 1.14 g/cm3Homework Equations [/B] This question...
  19. J

    Specific heat capacity and concentration

    Hello. I am doing a research paper on the relationship of specific heat capacity and refractive index of liquids. I am doing this by finding the relationship between specific heat capacity and concentration and refractive index and concentration. With this I can find a general trend and conclude...
  20. L

    Question regarding concentration units

    Hi all, I've done some experiments and I'm trying to work out the correct unit of my final concentration. The experiment goes thus far: I added 800 uL of a substance into a litre of my sample (800uL/L). This substance has a density of 1020 kg/m3 and is 60% w/w. I'm trying to work out the amount...
  21. L

    MHB Calculation of concentration unit

    I would like some help in working out the correct unit of concentration in the question below please. I added a substance which has a density of 1.020 kg/m3 to a sample at a rate of 800 uL/ L of sample The substance is also 60% w/w. Will the final concentration in the sample be in 490 ug/L or...
  22. D

    A Carrier concentration temperature dependence; semiconductors

    Hi all, I'm reviewing device physics and I would like to understand how majority and minority carrier concentrations for both N- and P-type substrates change with temperature. My reference, Pierret's Semiconductor Device Fundamentals, has this figure: and I want to generate curves for all...
  23. T

    What is the concentration of ions from Ksp?

    Homework Statement Homework EquationsThe Attempt at a Solution I am not too confident with my knowledge of Ksp so just checking my answer. Ksp = [Hg2+][S2-] Therefore root Ksp to get [Hg2+] = 1.2649*10-26. So answer is B. Is this right? Cheers!
  24. T

    Lowest concentration of ethanoate ions

    Homework Statement A small quantity of each of the following is added to separate samples of an aqueous solution of ethanoic (acetic) acid. Which would leave the lowest concentration of ethanoate (acetate) ions? sodium hydrogen carbonate solutiondilute hydrochloric acidmagnesiumdilute sodium...
  25. T

    Change in concentration in equilibrium caused by addition

    Homework Statement Cu2+ ions react with Fe2+ ions according to the following reaction. Cu2+ + 2Fe2+ --> Cu + 2Fe3+ At equilibrium, the concentration of Cu2+ ions is not changed by the addition of A) Cu2++B) Fe2+C) CuD) Fe3+. Homework EquationsThe Attempt at a Solution I chose A through...
  26. D

    Heterogeneous equilibria: concentration of solids issue

    Homework Statement Hello! Here is the quote from the chemistry textbook by Tro: However, since carbon is a solid, its concentration is constant—it does not change. Adding more or less carbon to the reaction mixture does not change the concentration of carbon. The concentration of a solid...
  27. A

    Question about acids And molarity vs concentration

    so is an acid like HCl, is it basically these HCl ions that are "dissolved" or "infused" into water and form an acid? So what I'm saying is HCl by itself isn't possible and it's only possible in the dissolved form or aqueas form. This would make sense because as far as I know an acid or base...
  28. Motivanka

    Understanding Concentration Calculations

    Hello! I have few questions regarding concentrations and I am really confused: 1. Task: How many cm3 of water should be added on 50 cm3 solution of glucose which has mass concentration 2 g/dm3 to get solution that has concentration 0,002 mol/dm3 ? So what happened is that I got correct result...
  29. N

    Courses Ohio State: Choose Physics Concentration for Sophomore Year

    Hello, I am starting my sophomore year at Ohio State university this upcoming Fall. I was recently trying to come up with a class schedule that fits my needs. Unfortunately, my school has many options that are really confusing to choose without consulting an expert, so I figured someone here...
  30. R

    Increasing the concentration of 30% H2O2

    Hi, I am in the process of calibrating our GC and one of the products we expect to find in our experiment is H2O2, but we only have 30% H2O2 in the lab. I can test 5% to 25% by dissolving further in water, so I can get some sort of calibration curve, but I'm stuck at 30%, is there a simple way...
  31. Vivan Vatsa

    How can I easily understand the relations between different concentration terms?

    I want to ask that how to understand the relation of different concentration terms. Like the relation of Molality, Molarity & Density & related relations of concentration terms. So how to understand the relations easily?
  32. G

    How to Determine the Concentration of I2 in a Solution Experimentally?

    Hi, We have been supplied an Iodine (I2) solution 0.005M.for an experiment but we are supposed to standardize the iodine solution (which i guess means that to find the exact concentration of the I2 solution) My idea is that we should do a titaration,but I don't know how to or what to do. So if...
  33. N

    Calculating the molar concentration of H3O+ and pH of solutions

    Homework Statement Calculate the the molar concentration of H3O+ ions and the pH of the following solutions: a) 25.0 cm3 of 0.144 M HCl(aq) was added to 25.0 cm3 of 0.125 M NaOH(aq) b) 25.0 cm3 of 0.15 M HCl(aq) was added to 35.0 cm3 of 0.15 M KOH(aq) c) 21.2 cm3 of 0.22 M HNO3(aq) was added to...
  34. A

    How to Determine the Mass of Iron in the Original Sample?

    Homework Statement 1.02 grams of an unknown sample, that contains iron and some other things. Amount of iron is unknown, other substances are unknown. The concentration is 0.023 mg Fe/mL The question says find the mass of Fe (in mg) in the 1.02 gram sample. Exact question is: "The unknown...
  35. B

    What is the Correct Value of Kw at 10°C?

    Homework Statement At 10 C, the concentration of OH in 1 M of HCl is approximately: Answer: 3x10^15 Homework Equations Kw=KaKb The Attempt at a Solution This answer throws me off. If we assume that HCl completely dissociates, we use the [H+] from the acid in the above equation: 1x10^-14 = 1...
  36. RoboNerd

    Question about light absorbance with liquid solutions

    Homework Statement A solution of Co+2 ions appears red when viewed under white light. Which of the following statements is true? A) a spectrophotometer set to the wavelength of red light would read a high absorbance b) if the solution is diluted, the amount of light reflected by the solution...
  37. ramzerimar

    Numerically find temperature in function of concentration....

    Homework Statement I don't even know if this is the correct forum for this question, but here we go. This exercise is from my numerical methods for engineers class, and it says the following: The coefficient of saturation of oxygen dissolved in fresh water is given by the equation: $$...
  38. F

    I Carrier Concentration in a Semiconductor

    Suppose I have an n-doped semiconductor and want to measure the electron concentration in the conduction band as a function of temperature. How would I go about doing this by measuring the Hall coefficient as a function of temperature, given that I don't know the electron and hole mobilities...
  39. A

    Making different concentrations of TiO2 using glycerin/H2O

    Hey fellow scientists.I have a burning question..I would like to make a similar chemical environment for sunscreen products with titanium dioxide present.Does anyone know the process of making different concemtrations of Tio2 paste using glycerin or water?i would really appreaciate some...
  40. B

    What is the ppm concentration of an aqueous solution with 0.0050% Ag+ ions?

    Homework Statement An aqueous solution is found to be 0.0050% Ag+ ions. Calculate the ppm concentration of the solution. Homework Equations 1mg / 1 L The Attempt at a Solution 0.0050%/100 = 0.00005g Assuming there is 1 L of solution .00005g *(1/1000) 0.00000005 mg/L 1mg/L = 1 ppm...
  41. B

    Understanding question : Concentration

    Homework Statement 63.0ml of a 1.70 M solution is diluted to a total volume of 248mL. A 124-mL portion of that solution is diluted by adding 167mL of water. What is the final concentration? Assume the volumes are additive Homework Equations What is going on in this equation? The Attempt at a...
  42. V

    How to calculate required concentration of absorbing agent

    Hi All, I am designing an optical solid phantom to represent tissue optical properties (scattering and absorption coefficients). I know what should be the optical properties of tissue but I don't how much absorbing agent should I add to the mixture so that the phantom exhibit my desired...
  43. T

    Machine elements stress concentration

    Homework Statement A flat part with constant thickness b is loaded in tension as shown. The height changes from 50 to 87 mm with a radius r = 4.0 mm. Find how much lower a load can be transmitted through the bar if the height increases from 50 to 100 mm and the radius increases from 4.0 to 10...
  44. C

    What is the concentration of starch in this example?

    Homework Statement [/B] I had 3 wt % starch concentration in 230 gram of water. During the experiment 100 gram of water was evaporated and gone. Therefore, 130 gram of solution was remained. What is the wt% concentration of the starch after water evaporation? Is my calculation sounds correct...
  45. C

    What is the concentration of my starch?

    I weight 7 gram of starch and added 3 gram of ethylen glycol and mixed it with 220 gram water. What is the final concentraion of my starch?
  46. H

    Easy Stoichiometry Concentration Problem

    1. A piece of iron was added to a beaker that contained 0.585 mol/L copper(II) sulfate, CuSO4(aq). The solid copper that precipitated was dried, and its mass was found to be 5.02 g. Some unreacted iron remained in the beaker. Calculate the minimum volume of the copper(II) sulfate solution. I...
  47. S

    Concentration of C6Cl6 in a sediment core w/ diffusion coefficient

    Homework Statement Exercise: Hexachlorobenzene (C6Cl6) is a highly toxic waste product of pesticide manufacturing. It is resistant to biodegradation. Sediments at the bottom of a reservoir in the Upper Mississippi River catchment have been found to contain high C6Cl6 concentrations. The...
  48. A

    Calculate the concentration (in M) of Cl- ions in solution C

    Homework Statement [/B] PROBLEM #1 You have 3.00 L of a 3.39 M solution of NaCl(aq) called solution A. You also have 2.00 L of a 2.00 Msolution of AgNO3(aq) called solution B. You mix these solutions together, making solution C. Calculate the concentration (in M) of Cl- ions in solution...
  49. K

    How do I find the ph without using Hasselbach's equation?

    Homework Statement hi so in my lab class we made a buffer solution by mixing 20.00 ml of 0.100 M Sodium Hydroxide and 40.00 ml of 0.100 M of acetic acid. We then poured 15ml of this buffer solution into a beaker. So we essentially have 15 ml of this buffer solution in the beaker. We then added...
  50. P

    Find the mass of Ag around the Nickel pole

    Homework Statement A nickel pole is put in an AgNO3 solution with volume 50ml and concentration 0.1 mol/litre until the concrentration is 0.02 mole/litre. Find the mass of Ag that is put around the Nickel pole. Homework Equations 2AgNo3+Ni->Ni(NO3)2+2Ag number of moles= concrentration*volume...
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