# 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. ### Chemistry Concentration of Phosphorus from KH2PHO4

Hi All, I am not sure if I am doing my math correctly. I am sure my method is jacked up but here is what I did: I mixed .5g of KH2PHO4 powder with 100 ml distilled water. From my poor understanding of chemistry I thought I would end up with a .5% solution or 5000 ppm. I then tried to...
2. ### Chemistry Calculating HCl Concentration in Solution

1% or 1.18 % (w/w) ?
3. ### Music Study with or without music?

Is it better to study with or without music?
4. ### Questions about the common-ion effect

I have two questions about the common-ion effect. Sorry if my terminology is not correct, I’ll try to be as clear as possible. My goal is to be able to understand what will happen to a solution of two compounds with a common ion, when subject to evaporation and temperature change. So, I really...
5. ### Physics puzzle about the concentration of fog droplets in the air

To estimate the concentration of fog droplets in the air, I thought of the mass of water in a given volume of air: I searched this value on the net, and I found that it is typically around ##0.05 g/m^3##. The mass of a single fog droplet can be calculated from its diameter and density. Assuming...
6. ### Concentrating Calcium Bicarbonate Solution

I want to increase the concentration of an aqueous calcium bicarbonate solution and have considered using 3A zeolite molecular sieves. I believe such zeolite uses potassium ions to make their pores smaller and is capable of exchanging the potassium for calcium, which I believe would make the...
7. ### Building an Affordable OD600 Sensor for Cell Concentration Measurement

Hi all, I'd like to make an home-built OD600 sensor for measurement of cell concentration in suspension by Optical Density. There are several spectrophotometers in the market, indeed quite expensive, so I am interested in realizing a cheap device with standard components. Here's an example on...
8. ### A Kirkendall effect: vacancy concentration and pair interaction energy

I am reading the following article on Kirkendall effect leading to the Formation of a hollow binary alloy nanosphere: a kinetic montecarlo study. I am unable to understand or find in references the reasoning to obtain equation (1):
9. ### Chemistry Units conversion for solution concentration

What are the units for C= p/RT where p is in Pa Would it be Pa J^-1 mol ? and if so, how could I get the concentration in mol/L
10. ### Programs Which physics concentration should I declare for my degree?

Hello. I am a non-traditional undergrad, currently conducting materials and electrochemistry research (optics, photonics, semiconductors, energy storage). Before going to college (post-secondary), I had extensive experience in bioinformatics and biomolecular research. Although it is not yet the...
11. ### Electron and hole concentration

I can't solve the following exercise: Assume for a certain non-degenerate semiconductor sampe at T = 300 K an intrinsic carrier concentration ##n_i = 2 \cdot 10^{13} \frac{1}{cm^3}## and the band effective densities of states ##N_C = N_V = 10^{19} \frac{1}{cm^3}##. 1. Determine the electron and...
12. ### Chemistry Calculating Molar Solubility of CaCO3: A Puzzling Problem

hello , i am solving a problem about solubility and the solution seems weird to me , the problem is the following : we are asked to calculate the molar solubility of (CaCO3) with (Ks = 5*10^-9) in water and in a solution of (NaCO3) with a concentration of 0,1M, knowing that (NaCO3) is totally...
13. ### Calculating CO2 Concentration For Pepper Spray Devices

I have a kid who wants to do a report on aerosols. As I understand, we have researched that for pepper spray devices liquid CO2 is used as a propellant, but we can't find out how they calculate the concentration. Is there a place we can find the right formulas needed?
14. ### A question about chemical equilibrium

Hello we learned about the chemical equilibrium and how to write it's formula in the case of liquid and gaseous phase , what about a reaction involving different phases ? like this one : how do we write the formula for the chemical equilibrium ? do we just ignore the carbon ,is there any rules...

16. ### Calculate Conductivity Temperature Dependence in Semiconductors

I have to plot the conductivity dependence of temperature and I have problems with obtaining the right dependency of \mu and n. But let's focus only on carrier concentration first. For n I used the third equation. From what I understand N_D is a constant. I want my plot to look like this: But...
17. ### I Can concentration gradients be related to information?

I was reading a great thread that pointed me to Robert Alicki, “Information is not physical“ (https://arxiv.org/abs/1402.2414). My that appeals to me, based on the apparent fruitlessness of understanding the system otherwise. But I don't know if it's even published, and even if "everybody has...
18. ### Chemistry Calculating initial concentration

(1)(25)=(x)(5) and x=5 (initial concentration of HOA) (x)(5)=(.200)(5) and x= 0.2 (initial concentration of BCG)
19. ### Particle Accelerator concentration

Summary:: What concentration for electrical engineering works on particle accelerators? What concentration for electrical engineering works on particle accelerators?
20. ### I Modeling the concentration of gas constituents in a Force Field

Say there is a gas made up of two gas molecules: Molecule A and Molecule B. Molecule A has a mass: ma and mole fraction: na. Molecule B has a mass: mb and mole fraction: nb. The gas is at thermal equilibrium and has a constant temperature throughout itself (T) everywhere. It is placed in a...

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22. ### Chemistry Chemical Equilibrium: find concentration from 2 solutions (ICE table)

Hello! I've recently encountered this problem https://www.physicsforums.com/threads/need-major-help.117630/ and solved it and I'm stuck at choosing between 2 solutions. I don't understand why do we need to plug in 0.39 and 0.65 to (1-2x) and NOT to (1-2x)^2. I mean, we were given 2NO2, not just...
23. ### Estimate the following quantities from a graph of the refractive index of NaCl

a) I managed to obtain some results that are roughly around what is given in the answers. Because \varepsilon_{st} and \varepsilon_{\infty} are values of \varepsilon_{1}, I used this approximation: n\approx \frac{1}{\sqrt{2}} (\varepsilon_{1}+\sqrt{\varepsilon_{1}^2})^{1/2} -> \varepsilon_{1} =...
24. ### Applied Physics Degree: Is It Misleading to Employers?

Summary:: I don't know I can say I have an "Applied Physics" degree, hoping for an engineering job. I am majoring in Computer Science & Physics with an Applied Concentration at my school. This essentially the Applied Concentration is dependent on the electives that I take in my Physics major...
25. ### I Defect concentration formula w/o Stirling approximation

In many cases, the concentrations of defects or charges are quite big enough to use SA, due to a big number of Avogadro's number. The derivation for the well-known formula of a defect concentration is followed. If the n_v is expected to be lower than 1, then it would be impossible to use SA...

A rectangle (plane strain/stress) is sheared on 3 edges (bottom fixed) so that it becomes a parallelogram. In theory this is pure shear and should undergo uniform deformation throughout the domain. The FEA result for this pure shear loading still shows stress/strain concentration on the bottom...
27. ### B How does the doping concentration affect the depletion width?

I do not understand why that is the case. Is there any intuitive explanation for it? Thanks
28. ### Concentration of electrolyte for the electrolysis of water?

I'm doing an experiment with the electrolysis of water, and I'm hoping to vary the electrolyte concentration (Epsom salt/MgSO4) to see changes in the rate of gas production. I was planning to just do intervals from no salt to maximum solubility, but was wondering whether there might be any...
29. ### The concentration of a solution is 4%

Hello I have an antimicrobial shampoo containing the active ingredient chlorhexidine gluconate at a concentration of 4% (w/v). Just say I wet my hair first then add 2 capfuls of the shampoo to my hair, does this dilute the shampoo to a lower concentration due to the water already on my hair, or...
30. ### Does DNA get affected by the concentration of the liquids around it?

Hi I would just like to know if DNA is affected by the concentration of liquids around it. Thanks and best regards,
31. ### Is the concentration of greenhouse gases proportional to the temperate

I can't seem to find an answer to this: If the present level of greenhouse gas concentration were not to change, would the temperature of the planet continue to increase? Or would it level off? Or is a continually increasing concentration of greenhouse gases required to keep raising the planets...
32. ### Diffusion current and carrier concentration equilibrium (unbiased)

Suppose you have a non-uniformly doped piece of semiconductor (without an applied bias) such that the acceptor dopant concentration Na(x) decreases from left to right (as x increases). In this case, the equilibrium hole distribution p(x) will not be uniform since then there would be a net drift...
33. ### Chemistry Calculating Concentration of Acid using a pH Titration Curve

Use the equivalence volume from the pH curve to calculate the concentration of the acid, HA. I'm not sure which equation to use or how to approach this question (Attached). Please elaborate on the steps on how to answer the question. Thank you!
34. ### Effect of doping concentration on the depletion width of p-n junction diodes

My question for now is as follows: Why does a high doping concentration causes a decrease in the thickness of depletion region. Any help will be highly appreciated! Thanks a bunch Regards!

37. ### B Relationship between wavelength and concentration of particles

What is the relationship between the wavelength produced by a laser and the concentration of particles in the air? Does the wavelength get larger if the concentration of particles the beam hits increase?
38. ### Chemistry Concentration greater than 100%?

Hello! When I want to convert 75% g/g of a solution to % g/ml, I get a concentration greater than 100%. it is right? is this possible?
39. ### Calculate the HCl concentration in H2O from the conductivity

Hi y'all, I think this is my first time in the chemistry section of this forum, so thank you in advance for your patience with what is (I'm pretty sure) an elementary question. I've googled around for this a bit, but my last acid chemistry study was in 2002 or so, so the reading I am doing is...
40. ### Equilibrium concentration of co2 in beer

Absolute pressure is gauge pressure + atmos press Guage press = 1.29 bar G 1 bar = 10^5 Pa 1.29 bar = 129,000 Pa Atmos Pres = 1.01x10^5 Pa Absolute pressure = 230,000 Pa Henrys law: P=KhC 230000Pa = (116x10^3Pa)C 1.98 mole fraction =C 70% CO2 = 1.387 mole fraction 44g Co2 in 1 mole 61.07g...
41. ### Calculate the equilibrium concentration of CO2 in beer in grams/liter

Absolute pressure = Gauge press + Atmos press Atmos press = 105 Pa Co2 press = 0.1 bar g = 10000Pa Abs press = 10,105 Pa Hydrostatic pressure = absolute press + (density)(grav)(height at midpoint) = 10,105 + (1008)(9.81)(10) 10,8989.8 Pa Calc CO2 conc by henrys law P=KHC C=P/KH =...
42. ### I Using Henry's law to calculate ammonia concentration?

We have a closed chamber of 20 liters. The bottom of this chamber is filled with ammonia solution of 5% (=2,7M/liter). The solution temperature is controlled at 40°C I would like to calculate the concentration of ammmonia in the chamber air, above the solution. It should be something with...
43. ### How to calculate Carrier Concentration vs. Depth from a CV measurement?

I'm trying to obtain the free carrier concentration vs depth profile from the CV (capacitance-voltage) measurements of a normally-on HEMT with the expressions used for a Schottky barrier, but I´'m confused about how to extract the values for depth. I found in textbooks and articles that the...
44. ### Atmospheric absorbance of CO2 and impact of increaseing concentration

This is a serious question, and it is not meant as an attempt to "debunk" greenhouse warming of the earth. Wikipedia has the below image, which shows the atmospheric transmittance as a function of wavelength. Notice the red vertical line through one of the CO2 absorption bands. We see that the...
45. ### Chemistry Why do we say that the concentration of solids and liquids are constant?

I was introduced to the concepts like molarity, molality , mole fraction, formality, normality etc. during general chemistry and it was said that these concepts are used to measure the concentration of solutions. But as the thing called Chemical Equilibrium came I was surprised when I read "In...
46. ### Chemistry Determining the concentration of ions in ppm

I'm a little confused by a basic statement in a paper I am reading. It says that calcium chloride (1 M) and sodium carbonate (1 M) i.e. equimolar, have "a predetermined concentration of 3500 ppm of Ca2+"... I understand that the mixing of these two will cause a precipitation reaction, but...
47. ### Tritium concentration at Fukushima Water Treatment Facility

Hello there, maybe I am wrong but I found something inconsistent between the espected tritium concentration in Newly RO Treated Water (6.7 10^4 bq/l --> graph at pag. 16 here) and last measurement published by Tepco on 22th of August at the Water Treatment Facility (1*10^3 bq/cm3) Converting...
48. ### Concentration of both buffers is the same, only the pH is different

Here I used Henderson Hesselbach equation in both the cases , I.e pH= pKa + log( [(PO4)3-]/ [H3PO4]) here pKa of phosphoric acid is 2.16 but the problem Is in both the cases the log part is same and Pka is also same so both will cancel out, and how can we solve? It is confusing.
49. ### Find the concentration of protons

After mixed, the volume is 200mL I am confused. The mol of H2SO4 is M*V 1M*100mL or 1M*200mL ? Finding the concentration of proton means the Molarity for H3O+ right? mol/volume H2SO4 + H2O -> H3O+ + HSO4- Mol H3O+ = Mol H2SO4?
50. ### Bulk concentration and concentration gradient

I have a membrane with a eutectic carbonate mixture and there is also OH- in the melt. I want to calculate the conductivity of the OH- using the diffusivity of OH- and the bulk concentration. How can I calculate the bulk concentration if I know that there is a concentration gradient of OH- and...