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 unknown concentration with delta H and delta S? [closed]

3-ethyl-4-methylhexa-1,3-diene undergoes a combustion reaction. For this reaction, the following concentrations were used: [O2] = 0.06 M, [CO2] = 0.09 M and [H2O] = 0.10 M. Determine the concentration ...
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36 views

Calculation of concentration at equilibrium for extraction

The equation for equilibrium of solvent-solvent extraction is: $$\ce{PhOH(toluene) <=> PhOH (aq)}$$ An aqueous solution contain $\pu{1.5 \times 10^{-2} M}$ phenol and is shaken with the same ...
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Determine the concentration, in mol dm-3, of the potassium manganate (VII) solution

Consider the following balanced equation for the reaction of potassium manganate (VII) with ammonium iron (II) sulfate. $\ce{5Fe^{2+} (aq) + MnO_4^-(aq) + 8H^+(aq) → 5Fe^{3+} (aq) + Mn^{2+} (aq) + ...
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1answer
32 views

Aluminum electrodes for NaCl [duplicate]

Upon using aluminium Electrodes for a concentrated solution of NaCl, i conducted electrolysis on the solution for nearly 4-5 hours. There was definitely a gas possibly hydrogen being evolved at the ...
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30 views

Converting number of peptide monolayers on a surface to mmol per meter square

I have the total number of peptide monolayers covering a surface (${x \times 10^{12}}$). I also have the surface area ($\pu{mm^2}$). What I need is to convert this to $\pu{mmol/m^2}$. How do I go ...
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2answers
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How do I prepare citric acid solution (from anhydrous powder) of accurate concentration, given that the solution volume expands when water is added?

I attempted to prepare saturated citric acid solution from anhydrous powder. According to online data, the solubility limit was 59.2 w/w at 20 °C, i.e. 59.2 g citric acid in 100 mL water. To ensure ...
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2answers
63 views

Is it valid to calculate concentrations given equilibrium constant and initial concentration?

Suppose we have the following reaction: $$\ce{2A <=> B + C}\tag{1}$$ which can be thought the sum of the following reactions: $$\ce{A <=> B}\tag{2}$$ $$\ce{A <=> C}\tag{3}$$ with ...
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Reversible equation in Chemical Kinetics — Should I use definite integral when solving the differential equation?

I found this problem: We have the following reversible reaction: $A \ce{<=>[\ce{k_1}][\ce{k_2}]} B $, described by the kinetics equation: $$\frac{d[X]}{dt} = k_1([A]_0-[X])-k_2([B]_0+[X])$$ ...
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How is molar mass of salt related to the concentration of a salt solution

I need to make a $\pu{10mL}$ $\pu{700ppm}$ salt solution. I know that $\ce{NaCl}$ will ionize into $\ce{Na+}$ and $\ce{Cl-}$ ions in water. Should I use the molar mass of $\ce{NaCl}$ ($\pu{58.44 g/mol}...
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69 views

Combining solutions with multiple concentrations - Mixing NPK fertilizer ratios

I'm trying to mix my own fertilizer to grow some peppers. Fertilizers are labeled with NPK ratios, so mixing two volumes and finding the result is easy: Just multiply the concentration of each ...
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1answer
32 views

Chromatography- why tM is separated from other peaks? [closed]

tM in Chromatography is the time of exist mobile phase. But, the mobile phase exist together with all the compunds that tasted in the process. So, why in the graph of signal to time we can see a peak ...
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1answer
164 views

Why are these two methods of converting from ppm to g/m3 equivalent?

I've found two methods to convert from $ppm$ to $g/m^3$. They both appear to give equivalent results, but I don't understand why. Can anyone join the dots for me and explain why they are equivalent ...
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1answer
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Find minimum solubilty of AgCN [closed]

i know it has to be solved by writing an equation between CN- conc and solubilty but i am unable to write a non-linear equation,any help is appreciated
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Is Molarity constant? [closed]

My friend and I were debating about if Molarity is constant in a disolution if this one changes volume due to evaporation. There was this problem that stated that 125 [mL] of sodyum chloride 0.122 [M] ...
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1answer
68 views

How does strong acids conduct electricity in water?

How do strong acids conduct electricity in water? I have just studied ionization of water and I'm confused about some points. First: I know that water ionizes in a very small amount ($10^{-14}$) so ...
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Is 1% m/m the same as 1% w/w?

Hydrocortisone cream seems to be sold as 1% w/w, but my cream is 1% m/m, which is confusing. Are they the same units or the same concentrations?
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1answer
58 views

What concentration is phenolphthalein indicator ? 1% or 0.1%

I read some information about phenolphthalein indicator, some websites suggested phenolphthalein indicator of 1%, others mentioned phenolphthalein indicator of 0.1%. What is the difference of both of ...
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Weight Percent Standard State

I am having one doubt in weight percent standard state...Please see the quote(Taken from the legendary thermodynamics book by David Gaskell): If deviations from Henry's law occur below 1 wt %,then ...
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Sensitivity vs. Limit of Detection of rapid antigen tests

I'm comparing a bunch of SARS-CoV2 rapid antigen tests: Columns 4 and 6 list the values for sensitivity and limit of detection (LOD). How come that a test with a several times lower limit of ...
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1answer
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Rate of change and kinetics order of reaction question

The rate of reaction is given by the following equation, where [Ker-S-S-Ker] is just the molecule being broken down and [RSH] is an abbreviation for thioglycolic acid The thioglycolate is in large ...
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Problem in the calculation of ionic strength of a solution

Recently I've been trying to answer the question 10-13 (c) of 9th edition of Fundamentals of Analytical Chemistry of Skoog et al. Comparing my answers with the student manual , I realized that my ...
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1answer
49 views

Why are some weak acid equilibrium approximations invalid in very dilute solutions?

Using two approximations for the dissociation of a weak acid, we can write $$K_\mathrm{a}= \frac{[\ce{H+(aq)}]^2}{[\ce{HA(aq)}]}$$ One of these two approximations we use is that the concentration of ...
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Why does the molar conductivity plot behave this way?

On the left image.. we see that specific conductivity is increasing at a decreasing rate, eventually plateauing as it reaches a maximum. I am unable to reconcile this with the molar conductivity graph ...
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1answer
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Why does osmolarity take into account both penetrating and non-penetrating solutes?

According to Wikipedia: … osmolarity takes into account the total concentration of penetrating solutes and non-penetrating solutes, whereas tonicity takes into account the total concentration of non-...
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Is 18:82 a valid ratio for Aqua Regia/(s)(nitrohydrochloric acid)? Source below

Here it writes that nitrohydrochloric acid (possibly Aqua Regia) is of the ratio of $18:82$, which is $1:4.56$ in a simpler form. On Wikipedia and every other source i found the ratio $1:3$. So what's ...
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Molarity of a mix between solid and solution

$\pu{50 g}$ of solid $\ce{NaOH}$ is added to $\pu{1.5 L}$ of $\pu{2.4 M}$ $\ce{NaOH}.$ Water is then added to the mix until the solution reaches $\pu{5 L}.$ I need to find molarity of the final ...
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are refractometers generic?

I need to check the presence (and also purity approx) of a substance in solution. I have a very good reference (10mg/1ml - the substance in water). Can I use a refractometer to do this? I am trying to ...
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Parallel reactions for one product

For me it is clear how I could solved the kinetic of a parallel reaction like this But, how can I solve if this would be the case: Thanks in advance!
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1answer
80 views

How to set up an ICE table for adding a weak acid to a strong acid

I am working on setting up an ICE table for adding 0.020 mol HCl to 1.0 L of 0.10 M propanoic acid. Since these are both acids (propanoic acid being the weaker one and HCl being strong), how would I ...
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Can I mix pressures and concentrations when finding equilibrium constant? [duplicate]

In order to find the equilibrium constant (or reaction quotient) I know I can find the value as the products over reactants raised to coefficient exponents. But, in all of the problems I have had to ...
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43 views

Deposition of saturated solution and affect of evaporated water

20g of water is evaporated from 200g of saturated solution of KNO3(aq) at 60°C by heating and the solution was cooled to 20°C. How many grams of KNO3 were deposited? The solubility of KNO3 in 100g of ...
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Effect of water vaporation on saturated solution

At a high temperature, water is evaporated from the saturated solution by heating. What is the solution losing exactly by the fact that the water left the saturated solution? Does it affect its ...
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2answers
191 views

When calculating the distance between molecules in a solution, is it reasonable to approximate a sphere around each molecule? [closed]

I am attempting to calculate the average distance between molecules in a particular concentration of a solution. My first instinct was to treat the solution as a system of spheres surrounding the ...
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Calculating stock solutions

In the question it mentions that the protein forms dimers. Does that affect the RFM of the protein when I use it in my calculations (10kDa). For example for part a, would it just be. 0.01/10, 000 = 1 ...
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1answer
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A question about ligand binding

I have done part a and part b but I keep getting a negative concentration for part c. For part a I got $\pu{2 \mu M}$ For part b I got $\pu{5.051 \mu M}$ For part c, I get $2=3.2 + \text{[bound ...
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1answer
51 views

Resulting ions concentration after mixing solutions

$\pu{1 g}$ of $\ce{NaHCO3}$ and $\pu{2 g}$ of $\ce{Na2CO3}$ were dissolved in $\pu{50 mL}$ of water known as solution A. Solution A was mixed with $\pu{450 mL}$ of $\pu{0.154 M}$ of $\ce{NaCl (aq)}$ ...
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1answer
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What does the equilibrium constant mean for reactions with very small concentrations?

When you calculate the equilibrium constant for a reaction with a higher concentration of reactants, the answer is fairly intuitive. For example, for the reaction: $$\ce{A + B <=> C}$$ Where we ...
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Using the method of differential absorption to determine the ethanol content of an unknown sample [closed]

I have completed a whole set of FITR-ATR spectra analysing 6 solutions of ethanol-water mixtures, all at different concentrations of each. I have now been instructed to use the method of differential ...
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Acorrect range of concentrations for the reactants in the equilibrium reaction

What would be a correct range of concentrations for the reactants in the equilibrium reaction, $\ce{Fe^3+(aq) + SCN-(aq) <=> FeSCN^2+}$? For a Chemistry project I am measuring the effects of ...
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Preparing aqueous solution of ethanol [closed]

You need to prepare $\pu{250.0 mL}$ of an aqueous solution of ethanol in the concentration will be $\pu{0.500 mol L-1}$. You have $\pu{100 mL}$ of a commercial solution of ethanol in water $(35.0\% \,...
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1answer
147 views

Plotting the data using Beer-Lambert law [closed]

For the spectroscopy lab we had a stock dye ($\pu{1.00E-4 M}$ Erioglaucine Blue) that we had to dilute. We had to dilute $\pu{1 mL},$ $\pu{3 mL},$ $\pu{5 mL},$ $\pu{8 mL},$ and $\pu{10 mL}$ in $\pu{...
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1answer
61 views

Finding concentration of hydronium ions in water after adding hydrogen chloride gas [closed]

A sample of hydrogen chloride gas, $\ce{HCl}$, occupies $\pu{0.932 l}$ at a pressure $\pu{1.44 bar}$ and at a temperature of $\pu{50^\circ C}$. The sample is dissolved in $\pu{1 l}$ of water. What is ...
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Performing a Redox Titration on a Vitamin C Sample Solution Containing Cellulase enzymes

I was wanting to performing an Iodometric Redox Titration on a Vitamin C sample solution created from allowing diced citrus fruits to sit in a water + cellulase solution. Because vitamin c is water ...
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Is is valid to compare reaction quotient to $K_p$ as well as $K_c$?

Can I use the reaction quotient compared to $K_p$ to answer the following question? The solid $\ce{XY}$ decomposes into gaseous $\ce{X}$ and $\ce{Y}$: $\ce{XY(s) <=> X(g) + Y(g)}$ with a $K_p = ...
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Kinetics of Decomposition of Hydrogen Peroxide [duplicate]

Consider the decomposition of Hydrogen Peroxide: $$\ce{H2O2 -> H2O + 1/2O2}$$ The rate law for this reaction is : $$\text{Rate} = k[\ce{H2O2}]$$ Further $$\text{Rate} = -\frac{\mathrm d[\ce{H2O2}]}...
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What is the size in m³ of a toxic benzene cloud when if 20.000 kg liquid benzene would vaporize?

Benzene is carcinogen, The short term exposure limit for airborne benzene is 5 ppm for 15 minutes see https://en.wikipedia.org/wiki/Benzene#Benzene_exposure_limits I would like to know which volume of ...
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251 views

Density of a sodium hydroxide solution

The specific gravity of a $50\%$ aqueous solution $\ce{NaOH}$ is $\pu{1.5298 g cm-3}.$ To my understanding, the $50\%$ means $50$ mass fraction $w,$ i.e. $\pu{500 g}$ $\ce{NaOH}$ in $\pu{500 g}$ $\ce{...
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1answer
174 views

Calculating the concentration of product in a solution based on the peak area of HPLC [closed]

Please help me resolving the following: A sample solution, $\pu{0.24mg/mL}$ Compound A, is exposed to heat to form Compound B. From HPLC data report I have peak area for Compound A and Compound B. ...
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2answers
57 views

How does the surface tension of water decrease with an increase in the concentration of NaCl?

Can anyone help me with the theory of surface tension? My chemistry experiment is related to the surface tension and concentration of NaCl. I am confused about my hypothesis. On the internet, I found ...
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1answer
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Concentration and Half Life of reactants A and B

Since reaction is first order with respect to both reactant A and B, I can write, $$ k=\frac{1}{t} \ln{\frac{a}{a-x}} $$ where a is initial concentration of reactant and a-x is remaining ...

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