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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Calculate concentration of reactant from the absorbance of product without molar absorptivity

I am given the reaction A → B, where the absorbance of the product B has been measured (see picture below). The initial concentration of A is $10^{-4}$ M. From the answer it is stated that one should ...
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Calculate rate constant of second order reaction and pseudo first order reaction

The reaction A + B -> Prod follows the second order kinetics. In an experiment, you initially have ten times as much B as A. The concentration of A varies with time according to the following data: ...
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The theoretical gradient of the nernst equation when changing concentration and measuring cell potential

How would I determine the theoretical gradient of the comparison of concentration vs cell potential. I am doing an experiment on this and achieved the experimental gradient but unsure as to how to ...
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Why is this equation true for a salt in acid?

I previously asked a question about a calculation (below) Calculate the molar solubility of $\ce{SrF2}$ in a solution buffered at pH = 2.00. ($K_{a}$ for HF is $7.2 \times 10^{-4}$). The $K_{sp}$ of $...
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Convention for writing concentration units

1st part of my question: Q) The concentration of an NaCl solution is 1M. Express this in percent wt. by vol. unit. Ans: $$\text{In %(w/v) unit}=\frac{58.5\pu g}{1000\pu{mL}}\times \frac{100}{100}=5.85\...
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Can you use more concentrated hydrogen peroxide solution for obtaining iodine from PVP-I?

In NileRed — Making iodine video Nigel Braun extracts iodine from the medical povidone-iodine. He says that the quantities of hydrogen peroxide needed is $\pu{500 ml}$ of $3\,\%$ hydrogen peroxide. I ...
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Determine reaction order of Cyclopentadiene

Reaction: $\ce{2 C5H6 -> C10H12}$ For this reaction it is stated that $\pu{0.609 M}$ cyclopentadiene was formed in an ethanol solution. When the solution was heated $(\pu{40 ^\circ C})$ and ...
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Diffusion of particles across a plane surface

A relatively viscous material is coated with a thin film consisting of gold nanoparticles that can diffuse into the material. We can assume that all particles have a diameter of $\pu{25 nm}.$ Coating ...
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How does concentration of the electrolyte changing over time affect the rate of electrolysis in sodium sulphate solution?

During the electrolysis of sodium sulphate solution, hydrogen is produced at the cathode and oxygen (from the hydroxide ion) is produced at the anode. Then I believe that the rate of electrolysis is ...
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How molarity and mass fraction are related? [closed]

Concentrated sulfuric acid contains very little water, only $5\,\%$ by mass. It has a density of $\pu{1.84 g mL-1}$. What is the molarity of this acid? I know to use the molarity $c$ is in $\pu{mol L^...
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How to make a mixture of a certain volume with x/y ratio mass?

For example for 1mL to get 3:7 mass ratio sand/water. I have multiple samples to make with different ratios but the same volume and I can't seem to find an ecuation for this. Thank you!
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How to prepare standard sample of benzene for gas sampling bag?

I need to make a 1 ppm gaseous standard of benzene in nitrogen gas within a Tedlar® gas sampling bag. Is this as simple as injecting 1 μL of neat benzene liquid into 1 L of nitrogen gas within the bag?...
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How much calcium hydroxide is needed to raise the pH of an aqueous sulphuric acid solution?

Lets say dissociation constants $K_{\mathrm{a}1}$ & $K_{\mathrm{a}2}$ of $\ce{H_2SO_4}$ in water are $1000$ and $0.012$ respectively. So the first dissociation step happens completely: $$\ce{ ...
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Relation between concentration and activation energy

Will increasing the concentration of the reactants in a chemical reaction increase the proportion of molecules with an energy greater than the activation energy $E_\mathrm{a}$? It seems to me that the ...
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Creating sodium tetraborate decahydrate from boric acid

I would like to obtain sodium tetraborate decahydrate (borax) from boric acid (note not the other way around that is answered here: Creating Boric Acid from Borax and Hydrochloric Acid) Perhaps use ...
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Finding final volume of the diluted solution with defined mass concentration given initial molar concentration

To what volume should you dilute $\pu{126 mL}$ of an $\pu{8.15 M}$ $\ce{CuCl2}$ solution so that $\pu{49.5 mL}$ of the diluted solution contains $\pu{4.56 g}$ $\ce{CuCl2}?$ I know you need to use $...
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Salt extraction from water without affecting mercury concentration

I am looking to theoretically bio-analyze a water sample regarding its mercury concentration from both sea and lake water using a biosensor with an enzyme biorecognition element. However, a big issue ...
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Will the rate of the reaction of discoloration of crystal violet change if I vary the concentration of crystal violet?

I'm trying to find a relationship between the concentration of crystal violet (limiting reagent) and the rate of reaction in the hydroxide medium. I've only seen examples of experiments varying the ...
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HCl labeled 31.45% concentration (20° Baume) [closed]

Just bought a standard concentration of HCl solution. The 31.45% is weight-by-weight & not weight-by-volume, correct?
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How would I find what specific wavelength I need to measure for a specific chemical in spectrophotometry (calcium perchlorate)?

I am currently doing a research project, and for it, I would like to use a photospectrometer to find the concentration of Calcium Perchlorate in my sample solutions. My current method of data ...
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Is the wavelength of light generated through a chemical reaction independent?

The chemical reaction in question is the reaction between Luminol and hydrogen peroxide. Is the wavelength of light generated through this reaction dependent on the concentration of either reactant? I ...
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Why does mercury(II) nitrate form only when using concentrated nitric acid?

In the reaction between mercury and nitric acid, mercury(II) nitrate only forms when concentrated nitric acid is heated up and added to it, if the acid is dilute, mercury(I) nitrate forms. I ...
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Osmolality and osmolarity of infant formula

Actually, this question is about the following sentence, which I have seen (in various forms) in numerous papers (e.g. this one and this one): The American Academy of Pediatrics advises that formulas ...
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Calculate concentration of product after time passed

If I have two parallel reactions: A --> P$1$ (k$_1$ = $0.00010$ s$^{-1}$) A --> P$2$ (k$_2$ = $0.00050$ s$^{-1}$) and know that the initial concentration of A is $0.0417$ M. How can I ...
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Calculating the concentration of reactants and products in parallel reactions after a time t

A substance A reacts with a solvent B to form an intermediate product IP. The reaction is bimolecular. The conc. of the solvent is constant at $12$M. IP can then react to form the two products P$1$ ...
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Determining reaction order from absorbance

A reaction is initiated in a solution which contained a dissolved component. The transmittance was measured at $\pu{240 nm}$ in a $\pu{2.54 cm}$ long cell. At $t = 0$ the transmittance was $1$. $\...
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Could Nernst Equation fail at high Ion concentration diffrence

When I was learning about neuroscience, I came across the Nernst equation and found out that it is only dependent on the quotient of the ion concentration outside compared to the inside. So, now I ...
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Why we are dividing rate of reaction with respect to a species by its stoichiometry coefficient to find rate of that particular reaction

If there is a reaction like this $$\ce{ H2 + Cl2 -> 2HCl}$$ I can understand that each individual species (reactant or product) can have different rates and we can compare them like this, $$-\frac{...
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How much solvent do you add for a 1:20 dilution, and why is it called 1 to 20? [closed]

A 1:20 dilution implies that you take 1 part of stock solution and add 19 parts of water to get a total volume of diluted solution equal to 20 times that of the stock solution So is ...
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Plotting second order reaction with different reactants

In a laser flash photolysis experiment, $\ce{C6H5NH2}$ $(C_0 = \pu{60 \mu M})$ is oxidize to its corresponding radical cations. There are three possible reaction pathways for the formation of the ...
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Is this true for conductivity of mixture of two solutions equal to the sum of conductivities of each solution?

Suppose $\ce{Na2SO4}$ has a conductivity $\pu{2.6 \times 10^{-4} S cm-1}$ and on mixing $\ce{CaSO4}$ to saturation, the conductivity becomes $\pu{7.0 \times 10^{-4} S cm-1}$. So, Is the conductivity ...
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Quantifying soapiness; there's pH, pKa and pO2, is there a p_soap or p_surfactance?

Yes, $\mathrm{pH}$ is a concentration, $\mathrm{p}K_\mathrm{a}$ is a dissociation constant, and $\mathrm{pO_2}$ is a partial pressure. These are (roughly speaking) ways to indicate how much of a key ...
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Calculating the weight of a chemical within a liquid mixture

I want to know the weight of ethylene glycol in a mixture of Shellzone 50/50 Antifreeze. I have taken the mid-range of 40-60% from the safety data sheet(SDS) for the amount of ethylene glycol in the ...
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Translating from milligrams in the pill to Ki at the receptor

Many places (e.g. Wikipedia) report the action of a drug on the various receptors, transporters, ion channels, and the like in terms of the Ki(nM). (This is for drugs that act primarily through such ...
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Why is the concentration of gases denoted in form of partial pressure? [duplicate]

In most of the chemical laws of chemistry involving concentration of products or reactants like equilibrium constant, reaction quotient, Henry's law, Nernst equation etc, I often see a similar note ...
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Hydrogen concentration measurement without gas chromatography

Please suggest ways to measure $\ce{H2}$ concentration in a sample of gas containing $\ce{HCl},$ $\ce{CH4},$ $\ce{N2},$ $\ce{CO2}$ and trace amounts of chlorosilanes without GC. The problem is that I ...
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Calculating molarity of iodine solution after reaction

I made an iodine solution referring to the methodology provided in this link: https://www.thoughtco.com/vitamin-c-determination-by-iodine-titration-606322 $$\ce{KIO3 + 5KI + 3H2SO4->3I2 + 3H2O + ...
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3 votes
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A physical meaning of the Danckwerts boundary condition in terms of concentration profile (adsorption)

Can someone please explain to me in a simplified way, what exactly does a well-recognized Danckwerts boundary condition do to the concentration profile of adsorption phenomena? I just cannot find a ...
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The effect of increasing concentration of a cathode solution on the voltage in a galvanic cell

I am having trouble understanding a concept. In a galvanic cell, where electrolyte A is zinc (in a solution of zinc nitrate) and electrolyte B is copper (in a solution of copper (II) nitrate), why ...
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Effect of addition of inert gas on concentration in an equilibrium [duplicate]

We have the following equilibrium established in a container with movable piston at atmospheric pressure. $$\ce{N_2 (g) + 3 H2 (g) ⇌ 2NH_3 (g)}$$ Now how does the concentration of the reacting species ...
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Rate of a reaction when volume of the system varies with time

Background I was solving this question from this book and I was not able to get any of the options. The gaseous reaction $\ce{n_1 A_{(g)} -> n_2 B_{(g)}}$ is first order with respect to ‘A’. The ...
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Relationship between molar mass and density in solids

In ideal gases, it's pretty clear that 1 mole of gas occupies 22.4 L at STP. By knowing this, it's easy to calculate density given molar mass. However, this isn't true for solids. If I know molar mass ...
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Calculating the ionic strength for an aqueous solution containing potassium ferricyanide and sodium sulfate

I have the $100$ microM of K$_3$Fe(CN)$_6$ is dissolved in water and the following data: $$\begin{array}{c|c} \text{Experiment} & \ce{[Na_2SO_4]}/\pu{M} \\ \hline \mathrm{A} & 0 \\ \mathrm{B} ...
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will splitting a solution will keep the concentration values (and moles) the same? [closed]

I have this exercise from my H.W: and I am asked: if we split the solution into 3 different containers equally - how many moles will the solution have in each container? will the Cl- concentration ...
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6 votes
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Discrepancy when calulating mol weights with ChemSketch and Python RDKit

I am an IT guy with little knowledge of Chemistry, so please bear with me... For context: I am working with a system that has a lot of structures, their .mol files ...
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Finding mass percent through molality of potassium nitrate solution

Question An aqueous $\ce{KNO3}$ solution has a molality of $\pu{4.16 m}$ and a density of $\pu{1.08 g/mL}$. Calculate the percentage by mass $\ce{KNO3}$ of the solution. My Approach I know that ...
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2 votes
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The effect of dilution on the rate of a system in equilibrium

I'm attempting to answer a question from my textbook, however the answer that the textbook provides doesn't make sense to me. The question: Laura, a VCE chemistry student, loves graphs and wanted to ...
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Is the rate of a zero order reaction always independent of the concentration of its reactants?

Consider the following reaction : $\ce{A + B}$ $\rightarrow$ $\ce{Products}$ where order of the reaction w.r.t. $\ce{A}$ is $-1$ and order of the reaction w.r.t. $\ce{B}$ is $+1$. So, overall order of ...
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Total concentration conversion

when dealing with waste water and the total values of P, N, C are given in ppm units, what molecular weight is used for converting from ppm to molar? for Example- what will be 12 ppm of P(T) in Molar ...
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More ions form pairs when concentration of acid increases, does that decrease the speed of reaction?

Electrical conductivity decreases as an acid becomes more concentrated because more ions form pairs. However, does that affect the speed of reaction of the acid as there is a smaller concentration of ...
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