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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 ...
Музаффар Шакаров's user avatar
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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? $$\ce{H2O <=> H+ + OH-}$$
ABC123's user avatar
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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 ...
Melissa Terry's user avatar
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1 answer
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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 ...
chef stu's user avatar
4 votes
3 answers
116k views

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 ...
Denis57's user avatar
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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 ...
Jenny's user avatar
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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 ...
Atharva's user avatar
2 votes
2 answers
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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 ...
mathnoob123's user avatar
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1 answer
5k views

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?
Fessie's user avatar
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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 ...
Atticus283blink's user avatar
3 votes
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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 ...
Hélène's user avatar
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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 ...
Mizaan Shamaun's user avatar
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1 answer
270 views

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 ...
Valeria's user avatar
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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 ...
Caesium-133's user avatar
16 votes
1 answer
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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.
user2997204's user avatar
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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 ...
CCC's user avatar
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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 ...
RandomPleb's user avatar
2 votes
1 answer
467 views

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....
Alex Smith's user avatar
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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 ...
Granger Obliviate's user avatar
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Should I round an experimentally determined reaction order to an integer?

For a lab experiment I did, I calculated the reaction order for one of the reactants using data from two trials, both rates, and the concentration of that reactant during each. $$ \frac{\text{Rate}_1}{...
Caesium-133's user avatar
0 votes
2 answers
861 views

Why do we assume that it is 1 mol?

A question in my book was as following: Benzine and chloroform are considered very toxic organic solvents that dissolve in each other and in a solution of benzine and chloroform there is 0.45 mol ...
Biker's user avatar
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What concentration (M) of citric acid should I use in a titration with 0.02M LiOH?

I am using an automatic titrator that records the amount of acid/base added and the pH of the solution in the form of a graph. I am trying to titrate citric acid to capture all 3 pKas in this graph. I ...
S. Vick's user avatar
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6 votes
1 answer
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How to approximate the pH of a box of water molecules with one proton?

I have a cubic box of length $L = 12.42\ \mathrm{\overset{\circ}A}$, containing $60\ \ce{H2O}$ molecules and $1\ \ce{H+}$ ion. How can I approximate the $\mathrm{pH}$ of the system? Following the ...
Sangkha Borah's user avatar
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260 views

How do I find the final concentration after an additional dilution?

I took poor notes and didn't record what the final concentration of an amylase solution I made last year. I recorded that I took $\rm 0.2\ g/10\ ml$ of the amylase solution, and then took $\rm 1\ ml$ ...
Ro Siv's user avatar
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0 answers
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Neutralization equation [closed]

If I have cider vinegar and want to calculate the total moles of acid found in it, how can I do it? I have the moles of NaOH and I know that it includes both acetic and malic acid but how can I ...
Shahad's user avatar
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9 votes
3 answers
929 views

Why is the equilibrium constant defined that way intuitively?

Suppose we have chemical equation: $$\ce{ aA + bB <=> cC + dD }$$ then equilibrium constant is defined: $$K=\frac{[C]^c[D]^d}{[A]^a[B]^b}$$ but why don't we define it as: $$K=\frac{cd[C][D]...
user153330's user avatar
5 votes
1 answer
2k views

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....
Tyrion Lannister's user avatar
1 vote
1 answer
13k views

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 $\ce{NaOH}$"?
frankenstein's user avatar
2 votes
0 answers
65 views

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 ...
user289661's user avatar
2 votes
0 answers
68 views

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 ...
Mrigank's user avatar
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2 votes
1 answer
98 views

How to dilute a stock solution when the resulting solution has a smaller volume? [closed]

Describe how you would dilute $2.0~\mathrm{L}$ of a $0.85~\mathrm{mol/L}$ magnesium hydroxide stock solution to make $200.0~\mathrm{mL}$ of $0.30~\mathrm{mol/L}$ magnesium hydroxide. I know the $$...
user24909's user avatar
0 votes
1 answer
933 views

Does the initial rate in the reaction of magnesium powder with nitric acid depend on the volume or the concentration of the acid?

For the question regarding the initial reaction rate, I don't quite understand why the answer is D. If I calculated the number of moles from the volume and conc, I would get A=0.4 moles; B=0.2 moles;...
CCC's user avatar
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0 votes
1 answer
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How to calculate a molar mass based on density?

I have been asked to calculate the molar mass and mole fraction of a 35 w/w% HClO4 solution with a density of 1.3g per ml. This is the equation I used to try to solve it: $\frac{1}{M} = \frac{0.35}{...
ohiliouh's user avatar
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5 votes
1 answer
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Creating Boric Acid from Borax and Hydrochloric Acid

I'm working on an experiment in school and I need to create 200 mL of 2 mol/L boric acid. According to a formula I found on wikipedia, boric acid can be created with a reaction with ...
Bob Marshall's user avatar
2 votes
0 answers
1k views

Absorbance vs titrant added in acid-base titration

I was working on this question: Nitrophenol is a colorless weak monoprotic acid ($\mathrm{p}K_\mathrm{a} = 7.2$) whose conjugate base is bright yellow. To $2.00\ \mathrm{mL}$ of a solution of $...
carbenoid's user avatar
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3 votes
2 answers
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Dissolving in DMSO semantics

What does it mean when a substance (powder) is 'dissolved in DMSO and used at $\mathrm{5~\%}$' Does is mean that the substance is first dissolved in DMSO and then added to another solution where it ...
Zigglzworth's user avatar
1 vote
1 answer
2k views

Partial and total concentration in solutions

The total pressure of gas mixture equals the sum of partial pressures of its components. Can this rule be true for liquid concentration? I.e. can we say: the total concentration of mixture is equal ...
Omar Al Bahra's user avatar
4 votes
0 answers
630 views

Calculating volume ethanol in an fermented aqueous solution of sucrose, water, and ethanol

I've been working on a biology experiment where I calculate the fermentation yield of yeast under various light induced stress responses inhibiting the translation of various fermentation enzymes. My ...
Mikey G's user avatar
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1 vote
1 answer
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Calculating molarity of a gas using ideal gas equation

Is hydrogen gas at 1 atm pressure and 298 K temperature considered as a 1 molar solution? If yes then can I use ideal gas equation $$PV=nRT$$ to find molarity as $$\frac nV = \frac P{RT}?$$
JM97's user avatar
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0 votes
1 answer
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How to calculate the concentration of the diluted solution given a source concentration in ppm?

A student adds $37.4~\mathrm{ml}$ of a $50.0~\mathrm{ppm}$ solution to a $100~\mathrm{ml}$ volumetric flask and dilutes to the mark. What is the concentration of the diluted solution? $13.7~\...
Jackel's user avatar
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1 answer
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How do we know that water has [H+] = 10^-7?

In the derivation of $K_\mathrm{w}$, the ionic product of water, it is stated that $$[\ce{H+}][\ce{OH-}] = K_\mathrm{w}$$ and substituting $[\ce{H+}] = [\ce{OH-}] = 10^{-7}$ we can find that $K_\...
Dimenein's user avatar
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1 vote
1 answer
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Mass of strontium iodide contained in a 350 mL solution

What mass (in mg) of strontium iodide is contained in $350\ \mathrm{mL}$ of a strontium iodide solution that has a concentration of $1.93\ \mathrm{µM}$? What I have done: $0.350\ \mathrm{L}\ \ce{...
Gᴇᴏᴍᴇᴛᴇʀ's user avatar
-1 votes
1 answer
707 views

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 ...
Gᴇᴏᴍᴇᴛᴇʀ's user avatar
-2 votes
2 answers
40k views

How to calculate the total concentration after mixing two solutions of differing dilutions?

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{...
Anasutashia's user avatar
1 vote
1 answer
4k views

Finding the concentration of a solution

Q.) Determine the concerntration of a solution made by dissolving 10.0g of sodium chloride in 750.0ml of solution. I did the following; 1mol of sodium chloride = 58.44 58.44*10 - 584.4g ...
Anasutashia's user avatar

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