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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Oleum concentration description

What is the meaning of "free" $\ce{SO3}$ and "combined" $\ce{SO3}$ in the oleum sample concentration description? Also what are these maximum and minimum values of % labelling in oleum sample?
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Does simmering sparkling water change/decrease its mineral composition significantly?

I know that heating sparkling water will cause it to lose $\ce{CO2}$. Does this have any other effects on the water that remains, such as reducing its mineral content? I understand when non-...
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How to determine concentration limits of a buffer that's limited by solubility?

I need to maintain a certain range of % of ionisation from a buffer. For e.g. Histidine buffer. When making high concentration of this buffer at (say) pH 7.2, 25'C, [concentration] is limited to 75mM ...
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Concentration of acid when titration has reached equivalence point? [duplicate]

I'm currently working with a lab report concerning titration. One of the tasks is to calculate the concentration of the weak acid ($\ce{HOAc}$) and the strong acid ($\ce{HCl}$) at the equivalence ...
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why do solids and pure liquids have no effect on yield and equilibrium? [duplicate]

There are three parts to my question. Part one: Let's assume we have a reversible reaction at equilibrium as follows : Calcium carbonate (solid) goes into calcium oxide(solid) and carbon dioxide(...
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2answers
6k views

Calculating concentration of H+ Ions using Ka Value [closed]

I have this homework question that I am a bit stuck on for an answer. If anyone could help that would be great. Question: For a $\pu{0.2M}$ $\ce{HNO2}$ solution ($\pu{K_a= 4.5 \times 10^{-4}}$) ...
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2answers
4k views

How to convert ppm to g/m3?

I'm not very comfortable with chemistry and I need to convert $\ce{CH4}$ concentration values in $\pu{ppm}$ to $\pu{g/m3}$. Is that possible? I've already researched a bit and realised that for water ...
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1answer
75 views

How do molecules know how to behave when a disturbance occurs in an equilibrium?

I am well aware of Le Chatelier's principle, but what causes molecules to behave in such a way, my guess is that it all has to do with rates of reactions and frequency of collisions. When at a ...
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44 views

Volume change of solute addition to solvent

When making and manipulating high concentration stock solutions of sugar excipients, is there a way to predict the corresponding volume effect that occurs? I am asking in order to be able to create ...
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1answer
740 views

Finding the molar concentration of reactant used

We were given this problem at my university, and I can't seem to figure out how it was solved. The question says we have $\ce{NaHCO3}$ and 100 ml of $\ce{HCl}$ react and one of their products is $\ce{...
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What is the point of using molality when we have molarity?

Molality and molarity are both concentration terms. Given molarity's popularity molality seems rather antiquated. Why is molality still discused in modern chemistry classes?
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How to correctly prepare a standard solution?

Having just spoken to my teacher about the creation of a standard solution, and she suggested one way of doing it, however a previous chemistry teacher had told us a different way of doing it. My ...
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141 views

Equilibriums and Overshooting

If we have some reaction $\ce{A(aq) + B(aq) -> AB(aq)}$ and right now we have less $\ce{A}$ and $\ce{B}$ then we would have at equilibrium, is there ever a time where the amount of $\ce{A}$ and $\...
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74 views

How do I measure out these salts using the proper method?

I'm planning on preparing a water solution using the following salts of reagent grade with approximately these concentrations: \begin{array}{lr} \ce{CaCl2} & \pu{10 mg/L}\\ \ce{Na2SO4} & \...
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1answer
725 views

What does “percentage by mass” mean in the context of a compound dissolved in a solution?

Copper can be recovered from low-grade ores by 'leaching' the ore with dilute $\ce{H2SO4}$, which converts the copper compounds in the ore into $\ce{CuSO4(aq)}$. In a $\pu{50 cm^3}$ leach solution, ...
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Why is the concentration of pure water is 55.5 mol/L?

Whilst reading about pH, it is given that concentration of water is $\pu{55.5 M}$. Let water be of $\pu{1 mol}$ at $\pu{297 K}$ and $\pu{1 atm}$ pressure. Then the concentration is $$c =\frac{n}{v} = ...
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1answer
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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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Should residual sodium be considered in measuring sodium content of sweat?

I read an article, "Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis", which describes the design of a wearable band that detects various components in sweat in ...
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1answer
208 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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Is it possible to extract mass concentration from DLS measurement?

DLS (dynamic light scattering) gives the particle size distribution (number percent vs. size) of particles in suspension. It also gives the count rate (cps, counts per second). Knowing this and the ...
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38 views

What is the molarity of a solution made by dissolving 25.63 grams of naphthalene (MM = 128.17g) in 250.0 grams of benzene? [closed]

I don't really understand how to find the amount of liters with benzene in order to find the molarity.
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Can I add the molarities of multiple solutes together?

If I am calculating the molarity of a solution in which more than one solute is dissolved, can I add the total number of moles of all the solutes together and divide it by the total volume of solvent ...
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Chemistry Calculation Dilutions of Acid

I was presented with the following problem in my lecture and I am confused as to what to do. You are required to prepare $\pu{250 cm3}$ of $\pu{0.100 mol dm-3}$ HCl by diluting $\pu{0.600 mol dm-3}...
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How to find mole fraction of solvent and solute in a vapor pressure lowering problem?

At $25$ degrees celsius, the vapor pressure of pure benzene ($\ce{ C6H6}$) is $93.9$ torr. When a non-volatile solute is dissolved in benzene, the vapor pressure of benzene is lowered to $91.5$ torr. ...
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145 views

Why doesn't hydroxide concentration equal concentration of carbonic acid and bicarbonate in a sodium bicarbonate solution?

To find the pOH of solution of $\pu{0.42 M}$ of $\ce{NaHCO3}$, given a $\ce{Kb}$ of $\pu{2.4E-8}$, my solution manual does the following steps: Reaction is similar to : $\ce{HCO3- + H2O <=> ...
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How to know the kinetic rate of one reaction from 3 tests with different concentrations?

Recently, I've run an experiment about the effect of reducing concentration on rate of a reaction. Here's the chemical reaction: $\ce{10 NaHSO3 + 4 KIO3 ⇌ 5 Na2SO4 + 2 I2 + 3 H2SO4 + 2 K2SO4 + 2 H2O}...
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How to calculate the gas-liquid interaction for dissolved HNO3 in water with air?

Thanks for reading this and (maybe) helping me in advance! I have to face the following problem: I have got $\ce{HNO3}$ dissolved in water (roughly $\pu{50\%}$) and I want to know how much $\ce{HNO3}...
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840 views

Can water be included in an ICE table if it is not the solvent and is a product?

The question that I have is whether you will count water in a Fischer esterification equilibrium problem where the equation is carboxylic acid + ethanol --> ethyl acetate + Water We need to find the ...
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1answer
488 views

How to calculate volume for NaOH and drano max gel (includes dilution and pH, pOH)

I have a question on an assignment that I don't quite understand. It says: What volume of $\pu{0.0100 mol/L}$ $\ce{NaOH(aq)}$ would have the same number of moles of hydroxide ions as $\pu{100.00 ...
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2k views

How to find volume of substance from molar concentration

The concentration of a substance dissolved in water $i$ is known in (mol/m3), so is the molar mass in (g/mol) and the density in (g/m3). I want to find the volume of this substance in m3. I have ...
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240 views

'Rate' in the rate law

I am slightly confused about what the rate is that is given by the rate law. Is it the rate of reaction (I.e. the rate of loss of reactant or formation of product divided by its stoichiometric ...
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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
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How do I calculate the equilibrium constant of a reaction from two related reactions' constants?

At a certain temperature the following reactions have the constants shown: $$\begin{align}\ce{S(s) + O2(g) &<=> SO2(g)} && K'_\mathrm{c} = 4.2\times 10^{52}\\ \ce{2S(s) + 3 O2(g)...
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Lugol's iodine 5 % aqueous solution

There is Lugol's 5 % solution with 5 g of pure iodine and 7.5 g of potassium iodide. In one ml there should be 12.5 mg of iodine in sum. But there are suggestions telling that two drops of this ...
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How to create a 3 M solution of ammonia from 25% ammonia

We have ammonia $25\%$. We also know $\rho_{\text{ammonia}} = \pu{0.86 \frac{g}{cm^3}}$, $\pu{25 ^\circ C}$. We want to produce $\pu{3 M}$, $\pu{0.5dm^3}$ ammonia. This means that there are some ...
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How do you calculate the heat of a reaction given a table of heat of formation values?

So I've been trying to answer this question, and as far as I've learned it's $\Delta H^0_{\mathrm f}$(products)-$\Delta H^0_{\mathrm f}$(reactants), multiplying each by number of moles and such. ...
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Finding the concentration of ferrous thiocyanate in calibration solutions

Concentration of $\ce{Fe(SCN)^{2+}}$ in calibration solutions Recall that the concentration of $\ce{Fe(SCN)^{2+}}$ in the calibration solutions is essentially the concentration of the $\ce{SCN-}$ ...
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how to calculate mols Ag from AgNO3 solution

Sorry for the very basic question but its been a very long time since I've taken chemistry and I'm having difficulty solving this problem. If I titrate something with 1 molar AgNO3, adding 50 ml of ...
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Will the reaction shift left or right?

The picture shows the correct answer. At Eq., I have: 3 Mol of A 1 Mol of B 12 Mol of C I was looking at each answer in terms of ratio of reactants to products, but its clearly not correct since I ...
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How to calculate concentration of unknown saturated stock solution from diluted solution whose concentration is known?

I want to measure the solubility of a compound. I prepared a saturated stock solution of my compound in 100ml of water by dissolving it in excess and filtering out the undissolved sample. Then I ...
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Calculate [Cr^3+] in equilibrium with Cr(OH4)- when 0.010 mol of Cr(NO3)3 is dissolved in a liter of solution buffered at pH 10.0

I tried setting up a RICE chart with the initial conditions being: $$\begin{array}{c|c} \hline \text{Species} & \text{Concentration / M} \\ \hline \ce{Cr^3+} & 0.010 \\ \ce{OH-} & 10^{-4....
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Chile 2017, One of the Largest Fires in South America: Wood Ash Derivates for Industrial Applications [closed]

Hi: We're a group of people who wants to help people, domestic animals and wildlife recovering from this fire. Summary: We're having in Chile one of the largest fires in South American history. More ...
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How to use C1V1=C2V2 How do the units work?

I am trying to do a dilution where I know I have 0.749 g/ mL and I want to use this concentration to calculate the grams of aspirin in each 100 mL solution. I am specifically worried about the units. ...
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657 views

Titration to determine the amount of hydrogen peroxide

I have a mixture of sodium carbonate, sodium bicarbonate, ammonium carbonate, copper (II) sulfate, hydrogen peroxide, and sulfuric acid. I'm titrating potassium permanganate against this mixture to ...
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1answer
941 views

Dilution question, “70 wt. % in H2O”? [closed]

If I have a solid and want to make an aqueous solution of 70%, how much water do I need? Is it as simple as weighing out 70 $\mathrm{g}$ of solid and adding water until I have 100 $\mathrm{mL}$? Will ...
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2answers
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Volume in decimetres cubed dimensional analysis

In chemistry class, we were learning about concentration, which is the number of moles of a substance per decimeter cubed of water, expressed as $\mathrm{mol} \cdot \mathrm{dm}^{-3}$. However, I was ...
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429 views

How does dissolving a hydrate affect concentration?

Say I have 0.72 grams of calcium chloride dihydrate. If I dissolve it in water, the 2 water molecules attached onto it dissociates just like the $\ce{Ca^{2+}}$ and $\ce{Cl-}$, right? And if so, ...
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Why is Ka constant when volume is increased?

The following graph shows $\ce{Ka}$ vs ${V}$ (Volume) at constant temperature, as ethanoic acid is diluted: However, I thought it would instead produce the following graph (see below). $\ce{Ka=[...
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Increasing available area of a solid will increase effective concentration?

If I say that making a solid reactant into a powder will increase the yield of the product, because it increases the available area of the solid, hence increasing its effective concentration. Is this ...
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le chateliers principle

One of le chateliers principle is effect of concentration change : When the concentration of any of the reactants or products in a reaction at equilibrium is changed , the composition of ...