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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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19 views

Why concentration of water is not taken 1 for the equilibrium constant of esterification reaction? [on hold]

For pure liquids and pure gases, we approximate the concentrations equal to 1. In case of the esterification reaction, why do we write $\ce{H2O(l)}$ in the $K_\mathrm{c}$ formula since we have ...
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0answers
19 views

How to find the molarity of Fe(NO3)3 in a stock solution made from multiple solutions [on hold]

A stock solution will be prepared by mixing the following chemicals together: 3.0 mL of 0.00200 M KSCN 10.0 mL of 0.200 M Fe(NO3)3 17.0 mL of 0.5 M HNO3 Determine the molar concentration of Fe(NO3)3 ...
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1answer
17 views

How to find concentration of three species from given molar absorptivities

If I am given the molar absorptivities of three species at a given wavelength, and I only have the concentration of one of those species, how can I determine the concentrations of each of the ...
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0answers
9 views

How to calculate pollutant mass concentration in exhaust air?

I want to calculate the mass concentration of methane in exhaust air as unit gram per cubic meter per hour. Assumed we have the following situation: A bioreactor ...
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0answers
28 views

What is the maximum concentration of HNO3 (nitric acid) which may be handled outside of a hood?

Commercial stock solutions of HNO3 (nitric acid) are usually 70% w/w, and according to several MSDSs (e.g. here), it is dangerous to inhale it: Symptoms/effects after inhalation : Irritation ...
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1answer
39 views

Calculate the Molar Concentration of HCO3− [closed]

As requested by MaxW, below is the exact problem that I was referring to: The equilibrium constant, Kea, is 5x10 mol/L for the reaction $$\ce{HCO3− <=> H^+ + CO3^{2-}}$$ The molar ...
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0answers
26 views

Adding Heat to food

So, I am trying to use Pure Caspsaicin to add a little heat to some food. Now the pure Caspsaicin has come in crystal form they are Lipophilic so I have to use Glycerin to dilute it. Now my issue. ...
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1answer
41 views

Confusion between moles and molarity units

I am a total newbie in the field and i would like some kind of guidance. So, I have been recently given 2 datasets with measurements regarding several phospholipid fatty acids of plasma HDL. Both ...
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1answer
21 views

How does the concentration of a gas affect the entropy of a system in a chemical equilibrium?

The question asks about factors that increase the entropy of the system. The mark-scheme states that "decreasing the concentration of a gas without changing the volume of the container" is the answer. ...
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0answers
9 views

How do I calculate the concentration using volume and absorbance? (Beer's Law) [duplicate]

Dilute the stock solution of KMnO4 to create several other sample solutions of known molarities. Fill in the data table below with the known concentrations.
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1answer
27 views

What is PPM in terms of air concentration?

When they say the $\ce{CO2}$ concentration is $\pu{350 ppm}$ what does this actually mean? Does this mean that if we took a sample of air say $\pu{1 m3}$ then $\pu{350 mg}$ of that cubic meter would ...
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1answer
28 views

Does molarity change if you decrease volume?

For example if the solute of the solution contains $\pu{0.5 mol}$ and the total volume is $\pu{0.5 L}$, the molarity would be $\pu{1M}$. But if I take a portion of that solution, let's say $\pu{0.1 L}$...
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1answer
53 views

How to derive rate law expression for inversion of sucrose with changing pH?

I came across a question worded as follows- "The inversion of cane sugar proceeds with half life of 50 minutes at pH=5 at any concentration of sugar. However, if the pH=6, the half life changes to 500 ...
3
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1answer
34 views

Homemade spectrophotometer to exemplify Beer-Lamberts law

I have built a 12-band spectrophotometer, and i'm currently keen on proving Beer-Lamberts law through a small practical example. The solution that I'm going to test with my spectrophotometer, is ...
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1answer
38 views

Diluting topical cream (10%)

I need to dilute a face cream with 10 % active ingredient to 2.5 % and 5 % but I am confused as to how. I looked into the $$c_1V_1=c_2V_2$$ and $$\text{concentration of a solution}=(\text{amount of ...
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1answer
316 views

Acetic Acid % in vinegar? Given average molarity of acetic acid

Question: The stockroom claims the percent acetic acid in vinegar to be $2.0\%$. The density of vinegar is $\pu{1.106 g {mL}-1}$. Using average molarity given ($\pu{0.2844M}$) calculate the mass ...
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1answer
54 views

How to determine the volume of water necessary to produce a solution with 4.9 g/l sulfuric acid?

The molar mass of sulfuric acid is $M(\ce{H2SO4}) = \pu{98.1 g/mol}$. We have $\pu{100 mL}$ of a $0.1$ molar solution of sulfuric acid. What volume $V$ in $\mathrm{mL}$ of water, $\ce{H2O}$, do we ...
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2answers
101 views

Is the mole fraction equal to the weight fraction?

Whenever there is a reaction is excess of air it is customary to assume mole ratio of $\ce{N2}$ to $\ce{O2}$ as $79/21$. However, in another reaction which states that it will contain $\pu{1 wt\%}$ of ...
2
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1answer
84 views

How to determine the proton concentration in the following solution in mol/L? [closed]

A $\pu{0.8L}$ solution contains $\pu{0.60 g }\ce{ NaOH}$ in water. Then the above question follows. It's been a long time that I made some chemistry exercises. Now I'm stuck with a couple of ...
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1answer
108 views

should charge balance be based on activities?

We have a fluid with $\pu{0.01 M}~\ce{HCl}$ and $\pu{0.02 M}~\ce{K2HPO4}$, so if we assume activity coefficients are $1$ throughout we can find pH as $6.800012$ and confirm that at that pH there is ...
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1answer
67 views

Maximum Concentration of Benzene possible

A question for my PhysOrg course states: Assume you are performing a reaction in which benzene is a reagent. What is the maximum concentration of benzene possible? Hint: what facts do you need to ...
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1answer
28 views

How many samples would be worth when following a desorption? How to relate with limit of detection?

I am following the desorption of a compound from a polymer. Let's imagine that it occurs at a certain rate and most of the compound is desorbed after 5 days (as in the figure). Then, I could use many ...
2
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1answer
52 views

Why does water diffuse from a lower solute concentration to a higher one?

I'm studying biology and this came up in the context of passive transport. I understand why, in general a gas moves down a concentration gradient (the random movement of gas particles and probability)....
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1answer
409 views

When using a “dilute hydrochloric acid” solution, how diluted should it be?

Quite often when reading through some instructions or documentation or an outline that I've found online (EG: acid-base extractions), theres a step that involves using a "dilute hydrochloric acid ...
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1answer
118 views

Calculate mass concentration of Ca(OH)2 solution

Can anyone help me calculate the mass concentration of $\ce{Ca(OH)2}$ solution with molar mass $\pu{74.1 g/mol}$ at the $\pu{pH of 12.8}$. My work so far: From the pH I get the molar concentration ...
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1answer
43 views

Amount concentration versus number concentration

The IUPAC Gold Book defines Amount concentration Amount of a constituent divided by the volume of the mixture. Also called amount-of-substance concentration, substance concentration (in ...
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0answers
16 views

EQPt pH of a Monoprotic Acid-Base Titration: Product of Molarites Over Their Sum

Context The Henderson-Hasselbalch equation is as follows. $$pH=-\log\big(K_a\big)+\log\bigg(\frac{[A^-]}{[HA]}\bigg)$$ One may follow its derivation in order to understand how it came to be, yet ...
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0answers
53 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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2answers
50 views

Does sheer amount affect reaction rates?

For example, in the iodine and starch reaction, if I use 20 mL of a set concentration of each, will it be slower to completion if I use 40 mL of each at the same concentration?
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1answer
31 views

Diluting two solutions together

I have two different mixtures: 1 gallon of "A mixture", which is 99% substance A and 1% water An arbitrarily large supply of "B mixture", which consists of 4% substance B and 96% water. How do I go ...
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3answers
76 views

What is the difference between “adding a liquid” and “diluting to a liquid”?

Place $\pu{20.0 g}$ $\ce{NaOH(s)}$ in a flask and dilute to $\pu{1.00 L}$ with water. Place $\pu{20.0 g}$ $\ce{NaOH(s)}$ in a flask and add $\pu{1.00 L}$ of water. How exactly do these two ...
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1answer
982 views

Does the concentration affect the voltage in electrochemistry

Hello for my final chemistry lab we are doing electrochemistry. For my independent lab I'm using 10mL of ZnSO4 and 10mL of CuSO4. Then connect them with a salt bridge. I connect Zn metal and Cu metal ...
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1answer
51 views

Calibration Ammonia Sensor and Gas Concentration

My name is Felipe and this is my first post here. I'm working on a project to calibrate an electrochemical ammonia sensor. But I have a lot of doubts because I am a layman in chemistry. I'll list them ...
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1answer
35 views

How to meausre ion interferences in solution?

Is there a way to quantitatively measure the interference of different metal ions in solution? I plan to measure concentration of Pb(II), Fe(II), and Cu(II) in solution together using a ...
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1answer
25 views

Find volume of sample such that it contains 100ng of DNA

Im struggling with the maths of concentrationsand volumes and things..Ill give the question, then my thoughts on it: A DNA trimer strand, ab, has moleuclar weight of $9309ng/\mu mol$. I#m designing a ...
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1answer
185 views

Percentage purity of Ba(MnO4)2 sample that completely reacts with given H2O2?

$\pu{40 g}$ $\ce{Ba(MnO4)2}$ (mol. wt. = 375) sample containing some inert impurities in acidic medium is completely reacted with $\pu{125 mL}$ of $\pu{3 M}$ $\ce{H2O2}$. What is the percentage purity ...
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0answers
61 views

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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2answers
60 views

Do we consider the dissociation of water when dealing with ion concentrations of a solution?

One mole of hydrated copper(II) sulphate, $\ce{CuSO4 . 5 H2O}$, is dissolved in water. How many moles of ions does the solution contain? 1) 1 2) 2 3) 6 4) 7 The ...
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0answers
34 views

Why are the results of two methods different for calculation LOD and LOQ?

I calculated the Limit of Detection (LOD) and Limit of Quantification (LOQ) with results (Table 1) obtained from HPLC (spiked muscle sample). For this purpose, I used regression analysis and two ...
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3answers
80 views

If i keep adding sulfuric acid into water, will it keep dissolving forever?

If i keep adding sulfuric acid into water, will it keep dissolving forever?
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1answer
666 views

What's the relation between molarity and molality?

I am trying to derive the relation between the molarity and molality of a solution Mole concept $\displaystyle n = \frac{M'}{M''}$ Here, ($n$) stands for number of moles $\ce{(M^{'})}$ stands for ...
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2answers
216 views

How to calculate molarity of a solution by solving the percentage?

Molarity is number of moles per litre of solution and we calculate it by simply dividing moles by volume. But, if moles are not given and the w/w or w/v percentage is given then, how can we solve for ...
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1answer
1k views

How do I solve questions pertaining to rate of disappearance and appearance?

In a reversible reaction $\ce{2NO2 <=>[$k_1$][$k_2$] N2O4}$, the rate of disappearance of $\ce{NO2}$ is equal to: $2\frac{k_1}{k_2}\ce{[NO2]}^2$ $2k_1\ce{[NO2]}^2-2k_2\ce{[N2O4]}$ ...
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1answer
303 views

Catalyst with zero order kinetics

I've read in a book that a catalyst may be included in the rate equation even though it is never used up. It was written as having zero order kinetics however I thought catalyst concentration will ...
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2answers
102 views

What is the ionization constant, $K_a$, of the acid?

A 0.45 M solution of a weak acid, HX, has a pH of 4.5. What is the ionization constant, $K_a$, of the acid? Attempt at solution: [HX] is already given as 0.45 M. [H+] is given by $10^{-4.5}$. ...
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1answer
133 views

What is the citric acid concentration, [HCit], in the lemon juice?

The pH of lemon juice is about 2.1. What is the citric acid concentration, [HCit], in the lemon juice? I am given that $HCit \leftarrow \rightarrow H^+ + Cit^-$ and that $K_a = 8.4 \times 10^{-4}$. ...
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1answer
959 views

Calculating the pH upon titrating barium hydroxide and hydrochloric acid

Question: Calculate the pH produced from mixing $\pu{25.0 mL}$ of $\pu{0.420 M} $ $\ce{Ba(OH)_2}$ with $\pu{125 mL}$ of $\pu{0.120 M}$ $\ce{ HCl}$. Attempt: I'm learning about acids and bases ...
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2answers
101 views

Diluting Stock Solution with NaOH

So I know that if you want to dilute a stock solution to a smaller concentration you simply use the $M_1V_1 = M_2V_2$ equation where the $M_1$ and $V_1$ are the molar concentrations and volumes of the ...
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0answers
101 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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1answer
52 views

Confusion about the ICE table

Calculate the pH of a $\pu{2M}$ $\ce{H_3PO_4}$.Calculate the equilibrium concentrations of $\ce{H_3PO_4 , H_2PO_4^{-} , HPO_4^{2-}}$. First equation: $\ce{H_3PO_4 <=> H^{+} + H_2PO_4^{-}}\ \ \...