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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How to calculate the concentration based on dilution of a stock solution?

One of my exam questions is about lipstick and calculating the amount of lithium in the lipstick by AAS. The determination took place by making standard solutions with known concentrations of lithium. ...
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What does “at%” mean and how it differs from “mol%”?

Sorry if my question is a bit obvious, but for some reason I'm getting confused with the percentages in this question: Concentration of $\ce{A}$ is $\pu{80 at\%}$ and concentration of $\ce{B}$ is $...
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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 ...
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Common ion effect

Let $\ce{HA}$ ($x$ molar) be a strong electrolyte and $\ce{HB}$ ($c$ molar) — weak electrolyte. As $\ce{HA}$ is strong electrolyte, it dissociates completely: $$ \begin{array}{lcc} \ce{&HA &-&...
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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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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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Should residual sodium be considered in measuring sodium content of sweat?

I read an article, "Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis", which describes the design of a wearable band that detects various components in sweat in ...
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Should I round an experimentally determined reaction order to an integer?

For a lab experiment I did, I'm calculating 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}...
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57 views

Given Kd find equilibrium concentrations of the reactants

$$\ce{Biotin + Avidin → Complex}$$ Biotin is a vitamin derivative that binds extremely tightly to avidin (a protein found in egg white) with a $K_\mathrm{d}$ of $\pu{1e-15 M}$. If you make a ...
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Emergence of Lognormal distribution for the concentration of chemical compounds

I'm currently reviewing the literature about lognormal distributions describing/approximating the variability of a given chemical compound across different cells/ samples etc etc. The main argument ...
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82 views

Calculate concentrations in a system made up of molecules in order to calculate ionic strength

I understand how to calculate ionic strength where there are concentration data in molality or molarity units available and where the system is made up of only two components. However, I have been ...
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NIOSH 7300 - ICP OES calculation

need some help with NIOSH 7300 method https://www.cdc.gov/niosh/docs/2003-154/pdfs/7300.pdf I have two 37mm cellulose filter paper, one is my filter blank while other is sample. The sample has 80L of ...
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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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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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How to determine concentration limits of a buffer that's limited by solubility?

I need to maintain a certain range of % of ionisation from a buffer. For e.g. Histidine buffer. When making high concentration of this buffer at (say) pH 7.2, 25'C, [concentration] is limited to 75mM ...
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le chateliers principle

One of le chateliers principle is effect of concentration change : When the concentration of any of the reactants or products in a reaction at equilibrium is changed , the composition of ...
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What is the difference between concentration and effective concentration?

What exactly is effective concentration in simple terms? From what I can understand it is the 'real' concentration taking part in the reaction instead of the concentration of the solute. Also, if I am ...
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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 ...
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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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42 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 ...
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620 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 $...
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Method for increasing concentration of extracts

I am using reagent grade propylene glycol (99.9% pure) and vegetable glycerin (99.7% pure) separately as solvents to extract certain active essential oils/molecules of various plant flowers. The ...
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302 views

Coffee and orange juice concentrations with a twist

This question dates back to a time where I used to watch something called The Curiosity Show... Kinda like Bill Nye the Science Guy's show. I just can't recall the answer to this so I'm hoping that ...
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59 views

Preparing CdSe electrodeposition bath

What is the best way of preparing an aqueous solution containing 5 mM $\ce{CdSO4}$, 1 mM $\ce{SeO2}$, 0.5 M $\ce{Na2SO4}$ and adjusting pH to 3 by adding 0.5 M $\ce{H2SO4}$? What is the ...
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How to calculate the amount of sodium sulfate needed to lower the silver ion concentration of a saturated silver sulfate solution?

How many moles of $\ce{Na2SO4}$ we have to add into a saturated $\pu{0.5 L}$ solution of $\ce{Ag2SO4}$ so that the concentration of $\ce{Ag}$ is $\pu{4.0 \times 10^-3 M}$? ($K_\mathrm{sp} = 1.4 \times ...
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35 views

Electrochemistry conditions for voltage to increase in a galvanic cell

I understand that increasing the concentration of reactants in a galvanic cell generally causes the voltage of the cell to increase. But is that really the case always? Consider a standard cell of ...
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36 views

Angels Share seems bogus

What is the explanation of barreled spirits (at 62.5% ethanol) that undergo changes in concentration of ethanol. Whereas the volume after aging is typically reduced, the proof varies between low 100 ...
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Viscosity and concentration of solutions

I will need a fluid around a specific viscosity, using a mixture of water and something like sugar. Is there a way to calculate viscosity based on concentration?
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What is the equation that describes the variation in concentration of an inhibitor in an heterogeneous catalysis?

I find myself in quite a pinch: I have to sustain a Chemical Physics exam, and I know for a fact that the professor often asks this particular question: Suppose that we have both a reacting species ...
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36 views

Arrhenius equation using concentration

I've been conducting some experiments to determine the temperature dependence of a reaction. To do this, I've been conducting the experiments at different temperatures and generated a graph of $\ln{[\...
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32 views

Reconciling these different solubility values

In a review article [1] on the solubility of CaCO$_3$(calcite), the solubility is reported to be on the order of 1 gram/litre. Since CaCO$_3$ has a molar mass of about 100, this solubility is ...
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174 views

Calculation of resultant pH

A solution with $\mathrm{pH}=4$ is mixed with a solution with $\mathrm{pH}=10$ in equal volumes. Calculate resultant $\mathrm{pH}$. Please note both solution consists of strong acids and/or bases i....
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Molar flux through membrane

Consider a liquid of pure $\ce{A}$ covered by a composite membrane through which the vapor of $\ce{A}$ is diffusing. The membrane consists of two layers of thickness $l_1$ and $l_2$. The diffusion ...
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How to convert from ppm to ug/m3 in case of PMx?

For $\text{PM}_{10}$, $\text{PM}_{2.5}$ sensors, sensitivity, minimum and maximum recordable concentrations are generally expressed in $\pu{ppm}$ (parts per million) while legislation uses $\pu{\mu g /...
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189 views

How does the molarity of a solution change on boiling off the solvent?

The dilution equation $$M_1V_2=M_2V_2$$ is an equation that can be used to calculate how adding water can impact the volume and molarity of a solution. So I was wondering if this equation would apply ...
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37 views

Colorimetry at home?

Is there a reasonably priced option for colorimetry at home? Is this even a good option to accomplish my goal? I'd like to roughly determine the concentration of a chemical in an ethanol extract from ...
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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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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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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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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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459 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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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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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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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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Volume change of solute addition to solvent

When making and manipulating high concentration stock solutions of sugar excipients, is there a way to predict the corresponding volume effect that occurs? I am asking in order to be able to create ...
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Molar Absorptivity of Copper(II) Sulfate

What is the molar absorptivity of copper sulfate? I am trying to find the molarity of copper sulfate solution by absorption in a spectrophotometer with a cuvette. However, I can't find $\varepsilon$, ...
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Is it possible to extract mass concentration from DLS measurement?

DLS (dynamic light scattering) gives the particle size distribution (number percent vs. size) of particles in suspension. It also gives the count rate (cps, counts per second). Knowing this and the ...
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How to know the kinetic rate of one reaction from 3 tests with different concentrations?

Recently, I've run an experiment about the effect of reducing concentration on rate of a reaction. Here's the chemical reaction: $\ce{10 NaHSO3 + 4 KIO3 ⇌ 5 Na2SO4 + 2 I2 + 3 H2SO4 + 2 K2SO4 + 2 H2O}...
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How to calculate the gas-liquid interaction for dissolved HNO3 in water with air?

Thanks for reading this and (maybe) helping me in advance! I have to face the following problem: I have got $\ce{HNO3}$ dissolved in water (roughly $\pu{50\%}$) and I want to know how much $\ce{HNO3}...
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Can water be included in an ICE table if it is not the solvent and is a product?

The question that I have is whether you will count water in a Fischer esterification equilibrium problem where the equation is carboxylic acid + ethanol --> ethyl acetate + Water We need to find the ...