# Questions tagged [concentration]

The concentration characterizes the composition of a mixture with respect to the volume of the mixture. There are mass, amount, number and volume concentrations. Related and within the scope of this tag are normality, molality, mole fraction/ratio, mass fraction/ratio.

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### Percent composition by volume of the reaction H2 + Br2 <=> 2HBr

For the reaction $\ce{H2(g) + Br2(g) <=> 2HBr(g)}$ at a certain temperature, $K=1$. Determine the composition (in per cent by volume) of the equilibrium reaction mixture if the initial mixture ...
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### Why don't we take into account the auto-protonation of water when measuring its concentration?

When we calculate the concentration of water at $25~^\circ\rm C$, why don't we assume dissociation of water at this temperature? $$\ce{H2O <=> H+ + OH-}$$
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### Calculating ppm of an ion in a solution

Calculate the ppm of $\ce{Fe^2+(aq)}$ if $\pu{0.0055 g}$ of $\ce{Fe(NO3)2}$ is dissolved in $\pu{2.0 kg}$ of water. I have tried converting g of iron nitrate into moles, using mole ratio between ...
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### Why do colored solutions become more transparent as volume is decreased?

For instance, I was drinking Gatorade, and as I drank more and more, the drink became lighter in color. Why? I don't understand. I would think that the molarity stays constant and the color too. I ...
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### How to convert from w/w% to molarity?

After reading a number of explanations about it after googling, I'm a bit confused on this. Some explanations are doing it using a solution density, others aren't, though most are. On one site it's ...
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### How to prepare solutions of different concentrations of potassium from stock solutions with different concentartions?

I need to prepare different concentrations of $\ce{K+}$ ($10$, $20$, $30$, $40$, $\pu{50 mM}$) by diluting a solution of $\pu{100 mM}$ $\ce{K+}$ with an isotonic buffer of $\pu{5 mM}$ $\ce{K+}$. I ...
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### Concentration and volumes

In the reaction: $$\ce{H2SO4 +CaCO3 \to CO2 + H2O + CaSO4}$$ Does altering the concentration of the sulfuric acid change the volume of the carbon dioxide produced [the volume of the sulfuric acid is ...
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### Change in gas phase reaction equilibrium when not all product and reactant are increased

$$\ce{2NOCl <=> 2NO + Cl2}$$ What will be the effect on equilibrium concentration of $\ce{NOCl}$ when equal moles of $\ce{NOCl}$ and $\ce{NO}$ are introduced in the mixture at constant ...
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### Do you include the "10 H2O" in the formula for borax?

When you calculate the mass of borax needed to make up a standard solution, do you include $\ce{\cdot 10 H2O}$ in the formula for borax? Why or why not?
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### What does the unit M stand for? [closed]

What does $\mathrm{M}$ signify in this pH calculation? To me, it just seems to be a random variable. For example: $\ce{[H+]} = 1.0\times10^{-7}~\mathrm{M}$ I am not sure what the $\mathrm{M}$ is ...
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### Why there is an Upper Explosive concentration Limit?

If we have a mixture of combustible gas (let's say it's methane) and air, what is the physical explanation for having a upper concentration limit? I found this document: Lower and upper explosive ...
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### Calculating the molarity of an acid solution

Concentrated hydrochloric acid is $37\% \ce{HCl}$ by mass and has a density of $1.2\rm~\frac{g}{ml}$. Calculate the molarity of a solution made by diluting $125\rm~ ml$ of concentrated $\ce{HCl}$ with ...
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### How does concentration affect The Position Of Equilibrium?

I was taught that when the concentration of the reactants is greater than the concentration of products then the position of equilibrium is shifted towards the left. However when I used La'Chateliers ...
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### Calibration of a spectrophtometer [closed]

In my lab, I had to use spectroscopy to determine the concentration of protein in milk whey from buttermilk and understand how absorbance of light is related to concentration (Beer's Law). This was ...
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### Getting the wrong pH value, according to data and online calculator

I'm doing a titration problem with a week acid and strong base, I used experiment data and an online calculator to check my answer, but my pH I calculated is a bit off. Can anyone see where I messed ...
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### What was the lithium concentration in 1940's 7-Up?

I just came across this article in the New York Times, where lithium (or more correctly, lithium salts), a known anti-depressant had been added to beverages in the 1940's. They also mention that a ...
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### Is the pressure of a gas proportional with the concentration of a gas?

Is the pressure of a gas proportional with the concentration of a gas? Because you can also use the pressure instead of the concentration in the equilibrium condition.
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### Solublity values interpretation

"Solubility: Soluble in water (>25 mg/ml), and DMSO (50 mM)." It happens to be talking about a drug but that's irrelevant to my question. Does this solubility statement reasonably indicate that I ...
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### Why can't we find the density and molarity given the masses of solute/solvent and molar masses?

From 2013 ACS Local Exam: We have a $\ce{KNO3}$ solution prepared in water, and we know the masses of solute and solvent as well as the molar masses. I know that we can easily find molality, but how ...
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### The temperature rise after neutralisation

The answer to this question is B, however, I don't quite understand. If considering Q= mc delta T, the heat released is to some extent being influenced by the no. of moles. If using that line of ...
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### Would adding acetic acid from household vinegar to washing machine make it too dilute to be effective?

Many people advise adding a cup of acetic acid (vinegar) to one's laundry during the clean cycle. From my calculations, considering one cup of acetic acid and a top gallon machine (at 40 gallons), it ...
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### Electrolytic conductivity vs metallic conductivity in a galvanic cell

I'm analyzing the current output of a galvanic cell with aluminum electrode in aluminum sulfate solution and platinum electrode in acetic acid solution. What I am confused about is whether molar ...
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### Can I convert from an emission amount (in tonnes per area) to a concentration (in ppbv)?

Hi, I was wondering if it is possible to estimate the concentration of SO2 given the total mass of SO2 emissions? Europa's EDGAR has a resource called "Global Emissions EDGAR v4.2" (see http://edgar....
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### How can I pass this concentration to ppm?

So the exercise gave us the concentration of a solution (1,5 x 10^-3 M) and the volume (10 mL). The 1st part of the exercise was to calculate the amount of volume we need from a more concentrated ...
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### Raoult's Law and Mole Fraction

Raoult's Law states that the partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture....
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### What's the difference between aqueous NaOH and dilute NaOH?

Dilute $\ce{NaOH}$ can be prepared by adding a suitable amount of concentrated $\ce{NaOH}$. What's the difference between "dilute $\ce{NaOH}$" and "aqueous $\ce{NaOH}$"?
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### What are the methods used to measure the concentrations of these anions?

Chromate and dichromate anions has the following equilibrium in acidic solution: $$\ce{2CrO4^2- + 2H3O+ <=> Cr2O7^2- + 3H2O}$$ How can one experimentally measure the concentration of each ion ...
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### pH, conc vs activity

After studying a somewhat overview of "gamma" activity coefficient (it is not actually in our course but may come in exam as a part of unknown paragraph in ionic equilibrium) I can understand most ...
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### Concentration of Iodide Ions in water

You add 10.50 g of solid lead(II) iodide to 525 mL of water. Assuming that the lead(II) iodide does not add to the volume of the solution, what is the concentration of iodide ions in solution? Here’s ...
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If you mix $\pu{20 ml}$ of $\pu{3 M}$ sugar solution with $\pu{30 ml}$ of a $\pu{5 M}$ sugar solution, what solution do you end up with? What I did, \begin{align} \text{volume} &= \frac{\text{...