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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What happens to an ongoing electrolysis when you turn off the battery?

Suppose you do an electrolysis experiment, where you have two carbon electrodes, a battery, and water in a which a strong electrolyte, like NaCl, is dissolved. The circuit is closed and the ...
dark_ursus's user avatar
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2 answers
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How does the concentration of H+ ions in HCl change as the pH changes? [closed]

I am helping my friend's 16 year old prepare for her GCSE chemistry exam. This question was on an AQA GCSE Chemistry past paper but I do not know the year and could not find a markscheme for it on the ...
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I am attempting to write a question here involving standard form 10 to the power -5. What do I use to enter this properly with? [migrated]

I want some help with a chemistry question about pH and concentrion .I am helping my friend's 16 year old. How do I write numbers in standard form with negative exponents in a question on this Stack ...
Judith Jones's user avatar
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Calculating mass of a solution

I am trying to calculate the mass of a specific volume of glucose 5% solution. I calculated the values for the components of the solution and wanted to seperately calculate the mass of the solution ...
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Different method of solving a question giving different answer [closed]

Calculate the concentration of nitric acid in moles per litre in a sample which has a density, $\pu{1.41 gmL^–1}$ and the mass per cent of nitric acid in it being $69 %$. I attempted to consider a 1L ...
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How to change molarity of hydrate group? [closed]

I am making stock solutions for an algal growth medium. One solution calls for dissolving 9 g of MgCl2 4H2O (Magnesium chloride tetrahydrate) to 50 mL of distilled water in an autoclaved bottle. My ...
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2 votes
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Deriving Nernst Equation for a hydrogen-oxygen Fuel cell

Reading across electrochemistry books (particularly the fuel cells chapter of the book "Alternative energy systems and applications" by Hodge) I came across the following formulae: $$\Delta ...
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Find the pH of a solution obtained by mixing 100 ml 0.1m Na3PO4 and 100 ml 0.1 M NaH2PO4. Given that H3PO4: [Κα₁ = 10^-4, Κα₂ = 10^-7, Каз = 10^-11] [closed]

So, my query is that since NaH2PO4 is a weak acid, and Na3PO4 is a basic salt, wouldn't they react? Another theory was that since NaH2PO4 is a weak acid and Na3PO4 is a salt of strong acid and NaH2PO4,...
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1 vote
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Acid base titration molar ratio [closed]

Consider the following neutralisation reaction: $$ \ce{2HNO3 + Ba(OH)2 -> Ba(NO3)2 + 2H2O} \tag{1} $$ I would be glad for help in how to solve this problem with $c_1V_1 = c_2 V_2$, because the ...
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Mass of gaseous ammonia required to prepare ammonia solution of a given pH

How many grams of gaseous ammonia do you need to make $\pu{200 mL}$ aqueous ammonia solution with $\mathrm{pH} = 11.34?$ As the mole ratio is the same for $\ce{H+}$ and $\ce{NH3},$ $$\ce{NH3 + H+ -&...
Allistor's user avatar
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How to calculate theoretical value of mass output using electrolysis with different electrolyte concentrations?

I am writing a research paper on a zinc-copper electrolysis experiment observing the mass output of Zinc on a copper cathode, in which I am changing the concentration of the zincsulfate electrolytic ...
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1 vote
1 answer
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Cesium Chloride Density Gradient Centrifugation and Isotopes

In Cesium Chloride Density Gradient Centrifugation, as used by Meselson and Stahl, Cesium ions can be seen as strongly affected by centrifugation, so much so that they can overcome their ionic bonds ...
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Will increasing the initial concentration of a reactant result in more time for the reaction to go to completion?

I understand that increasing the concentration of a reactant increases its instantaneous reaction rate, but shouldn’t the amount of time for the overall reaction to go to completion increase? For ...
Jay Jun's user avatar
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How to calculate the pH of a mixture of an acid with a buffered solution?

Being a physicist by training, having worked in software development for the last 10 years. Having heard my last chemistry lecture 15 years a go I am a bit lost in regards to how one can calculate the ...
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Determining the concentration of ammonium nitrate by chemical means

I have several litres of ammonium nitrate solution that I do not know the concentration of, but is approximately 0.6M. I don't have precise enough instruments to determine it via its density. I ...
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How do I explain that voltage decreases when increasing the concentration of the cathode in a voltaic cell?

I just finished a lab experiment in which I built a voltaic cell with copper (II) sulphate and zinc sulphate. My experiment was to identify the correlation between the concentration of copper (II) ...
Night's user avatar
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1 answer
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Iodine solution concentration

I am planning to make 1L of 0.005M iodine solution from KI and I2. I have found instructions that say to use 2 g of KI and 1.3 g of I2 but no explanation why exactly this particular amount. I also ...
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How to convert molar volume to volume?

This seems like a simple question that people must have asked already, but I can't find an answer online. I'm not a chemist, but need to use a code that deals with thermodynamics. I am trying to use ...
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Convert daltons (Da) to molar mass (g/mol) [duplicate]

This is probably a stupid question... In converting Da to molar mass (g/mol), Since 1 Da = 1 g/mol, is it logical that 64,776 Da = 64,776 g/mol or am I missing an intermediate calculation? Thank you!
burphound's user avatar
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Units of Activation Energy

Consider the reaction $$\ce{aA + bB -> cC + dD}$$ whose reactants are given by A and B and the products are C and D. Say the activation energy of this reaction is some $x$ joules/mole, But moles of ...
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"Is there any library in Python or software for analyzing raw chromatography data?"

I have taken the data directly from the FID sensor using a DAQ, so I have the chromatography data in this format: (2 data colummns in a txt file) (18000 rows) Time (s) Intensity (V) 0.00367___0.0008 ...
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Does real-world gas phase chemistry use "concentration reaction quotients" (K_c)?

As a theoretical chemist, my entire exposure to reaction quotients and equilibrium constants ($Q$ and $K$) is through thermodynamics ($\Delta G^\ominus = - RT \ln K_{eq}$ and so on). So as I started ...
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1 vote
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Concentration term PPM [duplicate]

What volume do we assume when the concentration is written as mass by volume ppm? I mean when mass by volume percentage is say 20%, we can say that 20g solute is present in 100 ml solution. So if it ...
Naman Singh's user avatar
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Determining whether precipitation will occur or not and finding the concentration of a specific ion in a solution

The Ksp value of AY2 = 9.148 x 10^-2. I am having problem with calculating the concentration of ions. And without the correct concentration I can't find the Qsp/Kip so I'm stuck without them I can't ...
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Determination of the chloride concentration by the modified Volhardt method

Would someone help me solve a task: The concentration of chloride ions in aqueous solutions can be determined by the Volhardt method. An excess of silver nitrate is added to the sample containing the ...
crvenikupus's user avatar
1 vote
1 answer
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A silly doubt on the concept of volume percent and concentration

I am trying to solve the following elementary problem of volume percent, however, I am not quite sure where my mistake is: Ethanol has a volume-by-volume concentration of 93.3%. Calculate the volume ...
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7 votes
6 answers
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Best regression model for a sigmoidal pattern

Students submit the data for an acid–base titration to my app. The abscissa axis corresponds to the volume. Along the ordinate axis are the pH values. The curve I’m looking for must work automatically ...
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Equilibrium Solubility of CO2 in Aqueous Solution and its Dependence on H3O+ Concentration

The equilibrium solubility of $\ce{CO2}$ in an aqueous solution is given by three chemical reactions: $$ \begin{align} \ce{CO2(g) &<=> CO2(aq)}\label{rxn:R1}\tag{R1}\\ \ce{CO2(aq) + H2O &...
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1 answer
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Are all salts completely dissociated in solution when put in smaller amounts than their molar solubility?

From what I understand, the solubility is given in terms of molar solubility (or $\pu{K_{sp}}$), from which it can be easily calculated). Indeed, the saturation point represents the maximum amount of ...
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Is it a convention to divide rate of reaction by stoichiometric coefficient?

If we consider a reaction $$ \ce{A + B -> 3 C} $$ The rate of reaction is given by $$ R= -\dfrac{\Delta[A]}{\Delta t} = -\dfrac{\Delta[B]}{\Delta t} = \frac13\dfrac{\Delta[C]}{\Delta t} $$ I know ...
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1 answer
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Relationship of acids and bases with pH. (Proportional Relationship) [duplicate]

Can someone please clarify the relationship between acidic-basic strength and pH? I have come across conflicting information and am unsure about the correct understanding. Some people including my ...
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1 vote
1 answer
95 views

Scrubbing methanol and ethanol from a gaseous mixture

I have a gaseous mixture (air) at a temperature of approximately 30 degrees Celsius in which the following gases are present: Oxygen 0 - 25% Carbon Dioxide 0 - 20% Methanol 0 - 100 ppm? Ethanol 0 - ...
DenmarkViking's user avatar
1 vote
2 answers
464 views

How to prepare solution of liquid reagent of the given molar concentration?

I have a liquid reagent with molecular mass $M = \pu{294.08 g mol^-1}.$ I'd like to prepare $V = \pu{400 ml}$ of solution of that reagent with a concentration $c = \pu{100 mM}.$ Does it mean I have to ...
Pono's user avatar
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-4 votes
1 answer
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Dilution formula for NH3 solution [closed]

I need this for an experiment: ca. 3 mL concentrated (15 M) aqueous ammonia solution, NH3 (from a dropping bottle.) I have the NH4OH pictured below. How can I dilute it to get what I need? What is the ...
Art's user avatar
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3 answers
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Why do we have to prevent the hydrolysis of iron(III) nitrate?

I want to make particular concentration of ferric ions from $\ce{Fe(NO3)3.9H2O}$, and then I found this video It says that we have to add nitric acid to prevent iron from hydrolysis, what does it mean?...
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Calculating concentration quotient and determining direction of reaction for equilibrium involving gases

I'm currently working on a chemistry problem involving chemical equilibrium, and I'm having some trouble figuring out how to calculate the concentration quotient $Q$ and determine the direction in ...
Steven's user avatar
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1 answer
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How does an equilibrium move when increasing the concentration of water?

I have the following equilibrium given: $$\ce{[Co(H2O)6]^2+(aq) + 4 Cl-(aq) <=> [CoCl4]^2-(aq) + 6 H2O(l)}$$ (I imagine the (l) for water is wrong, as the water is a part of the solution) The $\...
Rekeren1's user avatar
4 votes
1 answer
124 views

Chemical species equations in a kinetic mechanism of combustion

In combustion, for a kinetic mechanism involving $m$ reactions and $n$ chemical species, of the form \begin{align} \begin{cases} \nu_{11}' \mathcal{S}_1 + \nu_{12}' \mathcal{S}_2 + \dots + ...
Somestudent01's user avatar
2 votes
0 answers
28 views

How are gravimetric analyses of particulate matter performed, in order to determine particulate matter concentration in air?

I've been surfing Google Scholar a bit and learned that a common and comparatively less expensive method of measuring particulate matter concentration in air was analysis through gravimetric methods. ...
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How to find the added volume $V_e$

We have a volume $V_A$ of a solution of $\ce{CH3COOH}$ acid, its molar concentration is $C_A$ and it has $pH_0=3,4$, we add a volume of $V_e$ from distilled water to it, in this case it has $pH_0'=3,7$...
aymen aymen's user avatar
6 votes
1 answer
441 views

Does "brine rejection" happen for dissolved gases as well?

"Brine rejection" is the effect of sea ice pushing out dissolved salts, forming sweetwater ice and brine. I understand "freeze distillation", a method to concentrate alcohol in ...
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-1 votes
2 answers
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Why is molality measured in terms of the solvent instead of the whole solution? [duplicate]

The molality $b$ of a solute dissolved in a solvent is given by: $$b_\mathrm{solute} = \dfrac{n_\mathrm{solute}}{m_\mathrm{solvent}}$$ where $n_\mathrm{solute}$ is the amount of solute (e.g. in mol) ...
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3 votes
0 answers
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What is the goopy substance that forms before CaCO3 precipitates?

I do a lab where we mix a solution of sodium carbonate with a solution of calcium nitrate. As expected, calcium carbonate (white solid) precipitates out. However, if the concentration is high enough, ...
JLB's user avatar
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-2 votes
1 answer
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Find the w/w percentage nitrogen in an ammonium nitrate solution

MCQ Question: What is the w/w percentage of nitrogen (N) in an ammonium nitrate solution with a density of 1.05 g/cm3 and a molar concentration of 2.1 mol dm-3? (a) 2.8 % (b) 11.2 % (c) 16.0 % (d) 5.6 ...
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2 answers
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Finding unknown concentration using HPLC standard curve

I calculated a standard curve equation from a given concentration and peak area, which gave me $y=1994.6x+218.4$. I made the graph with the $x$-axis μg/mL and $y$-axis peak area. The question is, a ...
user131308's user avatar
-1 votes
1 answer
268 views

Calculate volume of hydrogen gas evolved

MCQ Question: Ammonia borane in water can release hydrogen upon hydrolysis while forming NH4BO2 as the other product. The volume (cm3) of hydrogen gas which will be evolved from the hydrolysis of 309 ...
Jane902's user avatar
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2 votes
1 answer
235 views

Finding concentration of ascorbic acid

Question: A person applied following procedure for the determination of ascorbic acid (Vitamin C) in a sample solution. A volume of 20.00 cm3 of the ascorbic acid sample was reacted with 25.00 cm3 of ...
Jane902's user avatar
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-3 votes
1 answer
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Even in an acidic solution with a pH equal to 0, there are only 1 mol/L H3O+ ions, while there are approx. 54 mol/L water molecules

I find this sentence in my high school chemistry book to be confusing: "Even in an acidic solution with a pH equal to 0, there are only 1 mol/L H3O+ ions, while there are approx. 54 mol/L water ...
Authentic Melody's user avatar
1 vote
0 answers
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Buffer solution of NaH2PO4 and Na2HPO4

We have this exercise without solutions From a 0.2 M $\ce{NaH2PO4}$ solution and a 0.2 M $\ce{Na2HPO4}$ solution, a buffer solution with pH = 6.8 is to be prepared. The total concentration of $\ce{...
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3 votes
2 answers
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Calculate the titer of a solution

I hope this is the right place to ask. We have this exercise without solution One litre of diluted sodium hydroxide solution (c = 0.15mol/litre) is to be prepared in the laboratory. The titer from ...
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