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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Finding the concentration of hydrochloric acid by titration

In a class experiment, $\pu{20 mL}$ of hydrochloric acid was diluted with distilled water to $\pu{500 mL}$. $\pu{20 mL}$ of this diluted solution was added to $\pu{20 mL}$ of $\pu{0.1 M}$ sodium ...
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How to determine the concentration of the acid solution by titration? [closed]

A student determined the concentration of a hydrochloric acid solution by titration with $\pu{25.0 cm3}$ portions of a $\pu{0.05 M}$ primary standard solution of anhydrous sodium carbonate. The ...
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1answer
35k views

How do I calculate the concentration of sulphuric acid by a titration experiment with sodium hydroxide?

In my latest chem lab the objective was to create a primary standard of $\ce{NaOH}$ and use it to determine the concentration of sulfuric acid. The first part of the lab was determine the molarity of ...
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1answer
21 views

What formula allows adjusting balance of (Ethyl Alcohol / Water / Caffeine powder) to know concentration for the Caffeine solution?

I am experimenting with different levels of concentrated caffeine solution. The solution has a small percentage of ethyl alcohol, in the $\ce{H2O}$. Problems encountered too much ethyl alcohol ...
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1answer
618 views

Can water volume reduce with introduction of another chemical [duplicate]

Can a chemical be introduced to a volume of water which can actually reduce the volume of water in that container?
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30 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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3answers
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How can a substance be diluted to nothing?

If I start with a small amount of a substance, and I dilute that substance with billions of gallons of water, what is the scientific explanation for there being no (actually zero) remaining molecules ...
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1answer
13k views

Effect of evaporation on the concentration of a saturated solution

When evaporating a saturated solution, does the concentration remain the same? My thinking is that because the solution is saturated, and the volume is decreased, the excess solute would precipitate ...
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17 views

Can isomers have different molar mass? [closed]

I was asked to research this question at school, but somehow none of the websites properly answer the question in yes or no.
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2answers
6k views

How to increase the concentration of HCl

Today I have purchased some $\ce{HCl(aq)}$ on my local market with a concentration of 23%. However, I need to obtain a concentration of 37% in order to perform an experiment. Can I use distillation ...
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1answer
4k views

Does the concentration affect the voltage in electrochemistry?

For my electrochemistry lab I'm using $\pu{10 mL}$ of $\ce{ZnSO4}$ and $\pu{10 mL}$ of $\ce{CuSO4}$ solutions connected with a salt bridge. I connect $\ce{Zn}$ metal and $\ce{Cu}$ metal to a voltmeter ...
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1answer
33 views

An exception to the IUPAC convention for italicisation (typography)

According to IUPAC, only physical quantities and variables must be italicised. Section 8 Use of Italic and Roman Fonts for Symbols in Scientific Text of ICTNS Guidelines for Drafting IUPAC Technical ...
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2answers
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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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854 views

What is the difference between chemical equilibrium and dynamic equilibrium?

Is chemical equilibrium and dynamic equilibrium the same thing? Both point to the reversible reactions and no net changes in the concentrations of product and reactant. Dynamic equilibrium from ...
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1answer
536 views

What was the lithium concentration in 1940's 7-Up?

I just came across this article in the New York Times, where lithium (or more correctly, lithium salts), a known anti-depressant had been added to beverages in the 1940's. They also mention that a ...
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1answer
57 views

Does the volume change when the reactions occur? [closed]

I have this reaction (all substances are gaseous): $$ \begin{align} \ce{A + 4.5 B &→ C + 2 D + 2 E}\tag{R1}\\ \ce{C + 7.5 B &→ 8 D + 2 E}\tag{R2} \end{align} $$ Does the volume change when ...
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1answer
51 views

How to dispose of NaOH solution? [closed]

I have a range of sodium hydroxide solutions with different concentrations. (from 1.0 mol dm^-3 to 0.5 mol dm^-3). The max volume of each is 100ml. How can you easily dispose of these? Can I pour them ...
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1answer
72 views

How to calculate the number of protons in a sphere given the volume and the pH?

The spherical radius of a nano-droplet of a solution ($\mathrm{pH}$ of which is $6$) is given as $\pu{20nm}$. I can find the molar concentration of $\ce{H+}$ and subsequently the number of $\ce{H+}$ ...
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1answer
40 views

Calculating the Ionic strength of sodium acetylsalicylate

With the addition of aqueous NaOH to an aspirin solutions in water the reaction will yield products of sodium acetylsalicylate and water. I would like to measure the amount of sodium apsirin formed ...
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1answer
69 views

Meaning of mass concentration “units” % m/v [closed]

In a saline solution that is 5.750% (m/v) potassium iodide $(\ce{KI}),$ there are: a) 5.750 mL $\ce{KI}$ per 100.0 mL $\ce{H2O}$ b) 575.0 mg $\ce{KI}$ per 10.00 mL of $\ce{KI}$ solution c) 5....
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2answers
98 views

Shouldn't mineral NPK fertilizer ingredients add up to 100%?

I use a mineral based fertilizer in powder form which - according to the label - should not contain any fiber and is fully soluble in water (I dissolved 2 times the recommended dosage and found no ...
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0answers
35 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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2answers
183 views

How to find the ionization constant of an unknown weak acid?

A $\pu{0.45 M}$ solution of a weak acid, $\ce{HX}$, has a $\pu{pH}$ of $4.5$. What is the ionization constant, $K_a$, of the acid? $\ce{[HX]}$ is already given as $\pu{0.45 M}$. $\ce{[H+]}$ is given ...
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2answers
53 views

Ratio of Water to Isopropyl Alcohol? [closed]

I am looking for a very simple formula to calculate the ratio of water to 99% isopropyl alcohol that I need to prepare a solution with a density of 0.925 g/cm3. I am assuming there is one.
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1answer
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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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1answer
42 views

Determining the hydrogen peroxide content in acetic acid [closed]

For a project I have to determine the peroxide content in some samples, for which we plan to use glacial acetic acid. Unfortunately, I don't know the peroxide content of my acetic acid and because we ...
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1answer
35 views

How to find osmolarity of a solution contatining salt and glucose?

What is the osmolarity of a solution that contains $4.00\%$ (m/v) $\ce{NaCl}$ $(M = \pu{58.44 g mol-1})$ and $3.00\%$ (m/v) glucose $(M = \pu{180.18 g mol-1})?$ I know you have to convert percentages ...
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2answers
64 views

Can the rate of reaction of a Voltaic/Galvanic cell be determined theoretically?

I am conducting a chemistry practical in which I measure the voltage of a Zn-Cu Voltaic cell over time. Assuming that the surface area of the electrodes are known, concentration of reactants are ...
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2answers
60 views

Finding molarity of hyposulfite solution used in titration

$\pu{0.1 g}$ of $\ce{KIO3}$ is treated with excess $\ce{KI}$ solution. The liberated iodine required $\pu{44 ml}$ of $x$ molar hypo solution. Calculate the value of $x$. I have used the equivalent ...
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1answer
4k views

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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1answer
78 views

Calculation of VOCs concentration (ppm) in the headspace of a bottle

What is the right way to calculate the concentration of volatile compounds in the air in a closed container? Suppose we have a $\pu{50 mL}$ bottle with $\pu{25 mL}$ of $100\%$ ethanol $(\ce{EtOH})$ ...
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1answer
3k views

How is sulfuric acid with a concentration of 12 M also 72% w/w?

According to LabChem, $12~\mathrm{M}$ of $\ce{H2SO4}$ is $72~\mathrm{w/w\%}$. When I try to convert $12~\mathrm{M}$ of $\ce{H2SO4}$ to $\mathrm{w/w\%}$ I get $117\%$ which is obviously wrong. $$\...
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2answers
670 views

Molality of the solution prepared from a hydrated salt [closed]

A solution is made up by dissolving $\pu{13.8 g}$ $\ce{Na2CO3 · 10 H2O}$ in $\pu{103.5 g}$ of water. What is the molality of $\ce{Na2CO3}$ in this solution? I can't solve it. I tried converting to ...
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5answers
17k views

Does the water in hydrates affect final concentration?

Say I have a hydrate, and I am going to dissolve it in water. Does the water in the hydrate affect the final concentration? Here's an example: If I have $\pu{249.69 g}$ of $\ce{CuSO4·5H2O}$, and ...
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2answers
387 views

How to convert P2O5 concentration to H3PO4 concentration?

Why are some elements such as phosphorus reported as $\ce{P2O5}$ concentrations when the materials have no $\ce{P2O5}$ in them. I would like an explanation of how the conversion is done between real ...
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1answer
492 views

How should I measure out a solution given in nanorods per ml to make a solution of a set number of mols?

I am trying to determine the number of nanorods that I would need to measure out to get a 1 mM solution. For the gold nanorods that we ordered, it was mentioned that the single nanorods dimensions ...
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1answer
61 views

10 g of NaCl is dissolved in 250 g of water. The mass fraction and molality of the solution is

10 g of NaCl is dissolved in 250 g of water. The mass fraction and molality of the solution is For calculating mass fraction, simply divided $10/250$ to get $0.04$. My book says it’s wrong. Is mine ...
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2answers
13k views

Electrolysis of diluted sulfuric acid

My teacher told me that electrolysis of dil. $\ce{H2SO4}$ (concentration below $50\%$) using inert electrodes results in gradual increase of the concentration of $\ce{H2SO4}$. I can't seem to figure ...
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2answers
355 views

Finding the value of pressure equilibrium constant

Question: A rigid vessel containing only $\ce{NO2(g)}$ is heated to $\pu{337^{ \circ}C}$ and allowed to come to equilibrium according to the following reaction: $$\ce{2NO2 <=> 2NO + O2}$$ ...
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1answer
77 views

Calibration Ammonia Sensor and Gas Concentration [closed]

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
56 views

Bracketing Standards and dilutions

You are running an ICP-MS (Inductively coupled plasma mass spectrometry), with bracketing standards of 10 ppm(mg/L) K+ and 100 ppm K+ and sample of 500 ppm, prepared 5 mL diluted to 100 mL. Shouldn’t ...
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1answer
45 views

Constant concentrations in solution

I'm a high school student considering the concentration of solutions, and whether the concentration is constant at the bottom or towards the surface. Even then, how would I know that the solution is ...
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0answers
16 views

Removing potash from water using poly-aluminum chloride

I have been conducting an experiment for a school project, (removing metals from water)I added 50 grams of sulphate of potash to 2 litres of water, then allowed it to dissolve for a 24hrs. On two ...
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37 views

Numerical simulation and calculations of pH

a. Reaction of $\ce{CO2}$ addition in water is as follows: $\ce{CO2}$ + $\ce{H2O}$ $\ce{->}$ $\ce{H2CO3}$ b. Then, pH of $\ce{H2CO3}$ solution is increased to 12 by addition of 1M $\ce{NaOH}$. ...
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1answer
207 views

How to convert micromolar concentrations into molar quantities, when the volume is also known

\begin{array}{c|cccccc} \text{Sample} & \text{Ammonia} & \text{Phosphate} & \text{Silicate} &\text{Nitrate + nitrite} & \text{Nitrite} & \text{Mn} \\ & (\pu{\mu M}) & (...
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1answer
438 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
40 views

Is the density of solute same as the density of solution? [closed]

This problem came up while solving some problems on mass percentage and mole concept. Essentially, our teacher said that the $w/w\%$ and the $v/v\%$ for a given solution will be the same, because in ...
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1answer
154 views

One mole of solute (NaCl) is dissolved in 1 litre water. The molarity of solution is [closed]

One mole of solute ($\ce{NaCl}$) is dissolved in $\pu{1 L}$ of water. The molarity of the solution is: A) $\pu{<1M}$ B) $\pu{>1M}$ C) $\pu{=1M}$ D) $\pu{=2M}$ My answer: It’...
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1answer
277 views

Can organic acids be concentrated and used like concentrated sulfuric acid and similar mineral acids?

Is it possible to make organic acids concentrated like inorganic acids like concentrated sulfuric acid and similar mineral acids?
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47 views

How would I find the molarity/concentration of a gas using pV = nRT?

The problem I'm working on is: At $\pu{1100 K}$ and a total pressure of $\pu{1 atm}$, $\ce{SO3}$ is $75.0\%$ dissociated. $$\ce{2SO3(g) <=> 2SO2(g) + O2(g)}$$ Assume $\pu{1.00 mol}$...