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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98 views

How does % purity on household products work?

For example, toilet bowl cleaner is 9.5% HCl. Does this mean that for every 90.5 moles of H2O (or other stuff) there is 9.5 moles of HCl? Does it mean that for every 90.5 g of H2O there are 9.5 g of ...
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1answer
334 views

Stoichiometry : dilution questions [closed]

I need 500 ml of 0.2 mol/L H2SO4 for a tutration lab. What volume in mL of the 18 mol/L stock solution should you use? I think this is a dilution question asking me to use C1V1=C2V2. I am confused ...
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655 views

Calculation of equivalent weight

When a solid element is reacted with chlorine, a gaseous chloride of vapor density $68.75$ is formed. If this reaction is performed at constant temperature and pressure, the volume of the system ...
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2answers
508 views

How to calculate molarity and the number of molecules for a mixture in a simulation box?

I want to do a simulation of a mixture which consists a total of $512$ molecules of glycine, ammonia, and water molecules mixture in a cubic box of, say, length $\pu{2.6 nm}$; $\pu{2.6 nm}^3 = \pu{17....
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2k views

Relationship between pH and volume

I had prepared two different volume of solution: $\pu{500 mL}$ and $\pu{100 mL}$ with same concentration ($1\%$), but I obtain different $\mathrm{pH}$. Will volume affect $\mathrm{pH}$?
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136 views

Neutralization of alkali solution by a mix of strong acids

$\pu{0.1 M}$ $\ce{HCl}$ and $\pu{0.2 M}$ $\ce{H2SO4}$ solutions are mixed in equal volume. This solution is diluted to double the volume. Find the volume of $\pu{0.1 M}$ $\ce{NaOH}$ which can be ...
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1answer
484 views

Mass of chromium in ammonium dichromate

What mass of chromium is in $\pu{100 mL}$ of $\pu{0.0400 mol/L}$ $\ce{(NH4)2Cr2O7}$? The specific concept is how to find the mass of a certain ion/element in a substance, given the concentration. I ...
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1answer
118 views

Calculating weight of soluble salt in a solution

I got a solution which density is $\pu{1.035 g mL-1}$ and it contains soluble salt $\ce{Ba(NO3)2}$ at concentration of $\pu{0.250 M}$. The teacher is asking from me to "clear" the solution from the $\...
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0answers
283 views

Why does [H3O+] of a buffer change very slightly when diluted?

I am confused as to why the [H3O+] of a buffer changes very slightly when diluted (at least in an intuitive sense). Consider: $\ce{HNO2 + H2O <=> H3O+ + NO2-}$ [$\ce{HNO2}$] = 0.45 M and [$\...
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What's a good way to find out how much lead is in parts being used in toys? [closed]

We are using parts from China in small-scale manufacturing of toys. We used an abotec "lead inspector" test kit on the same part from 3 sources, using abotec's leach test, in which we soaked each ...
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1answer
81 views

What are the molar and mass concentrations of 18% HCl? [closed]

A solution of hydrochloric acid of mass fraction $\pu{18.0\%}$ has a density of $\pu{1.0878 g cm-3}$. What are the molar and mass concentrations of this solution? I got $\pu{5.37e-3}$ and $\pu{195.8}$...
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210 views

Identification of a metal from group 2 [closed]

A chemist adds $\pu{0.115 g}$ of a group 2 element to water and the resulting solution is made up to $\pu{400 cm3}$ by adding distilled water. The equation for the reaction is shown below. $\ce{M}$ ...
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1answer
89 views

Concentration of mercury in body

Symptoms of mercury poisoning become apparent after a person has accumulated $\pu{20 mg}$ of mercury. If a person ingested $\pu{30 mg}$ of mercury, what concentration of mercury in parts per million, ...
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Should the concentrations in weight % of the components of a solution always add up to 100%?

There's a paper with this statement of a alkaline solution: Nanostructured CuO films were formed by immersing the cleaned tabs into a hot $(\pu{96 \pm 3 ^\circ C})$ alkaline solution composed of $\...
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35 views

pH at different concentrations

In making gummies with pectin, the pH is very important and needs to be at or below 3.4. USP indicates dissolving it in a 10% solution to test the pH, while some use a 50% solution. I'm told the ...
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1answer
4k views

How can you determine whether a solution is dilute or concentrated given its concentration?

How can you determine whether a solution is dilute or concentrated given its concentration? I don't whether this is a stupid question or not but I couldn't find any answer.
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96 views

Quantitative determination of chemical composition of a simple unknown mixture

Unknown mixture A [$\ce{H2SO4}$ and $\ce{CuSO4}$] Unknown mixture B [$\ce{H2SO4}$ and $\ce{HNO3}$] (ranged between $\pu{0.1 - 0.3 M}$ for the solution) (E.g. if you are using Unknown ...
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0answers
534 views

Calculating total volume mixing NaCl and water

I'm (as a non chemist) trying to calculate the the volume of a NaCl solution. The problem is that I know the volume of water prior to mixing in NaCl, but I want to know the volume of the solution ...
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1answer
104 views

How can I compare liquid concentration to solid concentration?

Total novice here! I'm trying to determine which is more sensitive between two drug tests, 1 that uses ng/ml and the other that uses pg/mg. Is there a way to standardize concentrations to compare ...
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2answers
1k views

How to calculate the concentration of the elements after dissolution of iron(III) chloride?

I was presented with the following problem: In the laboratory you dissolve $\pu{24.7 g}$ of iron(III) chloride in a volumetric flask in water to a total volume of $\pu{375 ml}$. What is ...
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1answer
180 views

Beer's Law: Are the graphs of concentration/time and absorbance/time supposed to look very similar?

For my lab, I'm trying to figure out if the reaction between NaOH and crystal violet is a zeroth, first, or second reaction. My slope is 5.714*10^4 and y-intercept 0.008016. In logger pro, after ...
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1answer
140 views

How to prepare phosphate buffer solution from mono- and disodium phosphate with a specific pH? [closed]

I want to prepare an aqueous solution of a mobile phase of $\pu{0.04M}$ Brij-35. The mobile phase has to be adjusted to pH $7.4$ with $\pu{0.5M}$ phosphate buffer which will be prepared with $\ce{...
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2answers
901 views

What causes the yellow colour in the Briggs-Rauscher oscillating reaction?

The color changes are due to different concentrations of supposedly $\ce{I2}$ (which causes the yellow/amber color), $\ce{I-}$ (colorless) and $\ce{I3-}$ (dark blue). Since iodine ($\ce{I2}$) is ...
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6answers
5k views

Why is the specific gravity of 0.9 % saline 1.0046?

Medical Normal Saline (0.9% Saline) contains 9 g of salt dissolved in 1000ml of water. Hence a litre of NS should weigh 1.009 kg. Hence its specific gravity should be 1.009, but it’s only 1.0046. (I'...
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Looking for a theory predicting conductivity values of electrolytes at higher concentrations

I'm looking for a theory to calculate the electrical conductivity of electrolytes, namely $\ce{NaCl}$ and tartaric acid ($\ce{C4H6O6}$) dissolved in water, depending on their concentration. The only ...
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1answer
339 views

Reverse reaction of acid dissociation [closed]

Consider an acid HA with Ka 10^-10 dissociating into its ions as HA⇌H+ +A- My question is-if we introduce solution of pH=3(let's say any weak acid or a buffer) and put ions of A- of 0.1M into it (...
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1answer
456 views

Propylene Glycol as a water main anti-freeze

We are a young student science group looking for solutions to real world problems. We are currently working on ways to keep our city water mains from freezing in the winter. Our team is researching ...
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1answer
401 views

Concentration of a solution of NaOH

I'm about to try to make my own soap for the first time. In order to create my recipe, I'm using this calculator. As I'm using a lye solution, I have to fill the box %w/w of the solution. The ...
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1answer
133 views

How does the use of inert gas in fluorination of saturated aliphatic hydrocarbons make it less violent?

While studying alkanes, I found this written in my book: Fluoridation can be achieved without violence when alkane is treated with fluorine diluted with an inert gas, or by the action of inorganic ...
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0answers
454 views

Series of dilution without a constant dilution factor?

I have to make a series of dilutions though the dilution factor is not constant. I'm trying to understand how to carry out this dilution in the most efficient way as not to waste much solution. ...
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0answers
1k views

What's the actual difference between Formality and Molarity?

Today, I came across a question: "State the differences, in not less than 5 points, between Formality and Molarity". Using my knowledge, I wrote down 2 points, and stretched it to 3 somehow, but that'...
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1answer
2k views

How do I work out the original concentration of a solution after taking an aliquot and further diluting it for analysis?

I'm trying to work backwards to obtain the original concentration of a 1 litre solution. I feel my calculations have gone wrong and need another set of eyes to have a look. To start, a tablet ...
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1answer
613 views

How can I calculate the concentration of ethanol vapor in an airstream?

How can I calculate the concentration of ethanol vapor in an airstream? The steady state generation flow rate (of the vapor) is 625 ft^3/min. The ambient temp is 50-60 F (we can use avg temp 55 F). ...
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1answer
7k views

Titration with Ca(OH)2

In the laboratory, $20.0$ milliliters of an aqueous solution of calcium hydroxide, $\ce{Ca(OH)2}$, was used in a titration. A drop of phenolphthalein was added to it to indicate the end point. The ...
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2answers
993 views

Questions on concentration [closed]

Currently I am attempting two questions on concentration but I am not sure if I am correct. Can someone help me with these questions? These are the questions: 1) Calculate the volume of pure water ...
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0answers
37 views

Equilibrium involving water and solid component

$$\ce{A + B <=> C(s) + H2O(l)}$$ Why when $\ce{H2O}$ is liquid and $\ce{C}$ is solid, the equilibrium constant of the reaction is $$K_\mathrm{eq} = \frac{1}{[\ce{A}][\ce{B}]} \quad ?$$
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530 views

Determining the purity of commercial NaCl

I am trying to figure out how to determine the percentage of NaCl in salt. My purpose is to be able to test the purity of salt that I received before washing so that I can determine the quality of the ...
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1answer
108 views

Optical techniques for kinetics studies

What optical methods can be used to measure the concentration of reacting gases in a reactor during an exothermic and fast reaction? I need to monitor and measure the local concentration of my gases (...
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1answer
480 views

calculate the number of shots of Captain Morgan’s rum

I am facing a challenge, and this is my first question in this stack exchange. I have worked out the following problem but the answer I got (number of shots) is ridiculous. Could any of the chemist ...
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0answers
91 views

SO3(2-) to Na2S2O5 ratio

Is there a way of calculating the amount of sodium metabisulfite from the sulfite content? I found online instructions for the test kit for sulfite that suggests multiplying by $2.37$ to obtain $\pu{...
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1answer
976 views

Determine reaction concentration at chemical equilibrium with multiple reactions

I have a problem understanding how to calculate the change/dependence of the concentrations at the chemical equilibrium using multiple reactions. The concentration of my reactants and products at ...
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1answer
433 views

Do I use the Nernst equation when the concentrations of electrolyte in both half cells are equal?

I'm doing a chemistry report, and for my experiment I investigated the amount of voltage produced by different half cells in a voltaic cell. However, I tested them under nonstandard conditions as ...
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2answers
2k views

What source of error in an acid-base titration could lead to a higher reading of the acid concentration?

Methanoic acid ($\ce{HCOOH}$) is found in stinging nettles. In an analysis of the concentration of methanoic acid in a solution extracted from nettles, the solution was titrated with a standard ...
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0answers
457 views

How can I calculate the concentration of nanoparticles in water solution? [closed]

I have synthesized gold-silver bimetallic nanoparticles in water media by following this article. How can I calculate the concentration of my nanoparticles solution?
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743 views

Is 70% ethanol hygroscopic?

I'm currently doing some DNA extractions and I realized that in some protocols, they are saying that ethanol is hygroscopic. In this source, they are saying: 85% ethanol made with nuclease free ...
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1answer
35k views

What is the relation between molarity and molality? [closed]

Is the following equation correct: $$m = \frac{1000 \times M}{M \times M_b - 1000 \times d},$$ where $M$ - molarity, $m$ - molality, $d$ -density of solution, $M_b$ - molar mass of solute?
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1answer
152 views

Etymology of “normality”

Why the concentration of a solution expressed in gram equivalent weights of solute per litre of solution is termed as "normality" ? Does it have anything to do with the word "normal" ?
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1answer
593 views

How can I calculate the molar conductivity of a solution with multiple solutes?

I'm running an experiment mixing 2 different solutions, $\pu{5 mL}$ of $\pu{0.1 M}$ $\ce{NaCl}$ with $\pu{5 mL}$ of $\pu{0.1 M}$ $\ce{KCl}$. I am measuring the conductivity of the total solution in $\...
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1answer
281 views

Why does the conductivity of a LiOH solution decrease when boric acid is added?

If I start with pure water and add $\ce{LiOH}$ the conductivity of solution increases. However, if I then dissolve boric acid in the same solution the conductivity falls. I would have thought adding ...
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1answer
540 views

Oleum concentration description

What is the meaning of "free" $\ce{SO3}$ and "combined" $\ce{SO3}$ in the oleum sample concentration description? Also what are these maximum and minimum values of % labelling in oleum sample?