A message from our CEO about the future of Stack Overflow and Stack Exchange. Read now.

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.

Filter by
Sorted by
Tagged with
-1
votes
1answer
2k 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 $\pu{0.1 L}$...
-2
votes
1answer
278 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 ...
2
votes
1answer
58 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 ...
1
vote
1answer
326 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 ...
-1
votes
1answer
3k 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 ...
0
votes
1answer
70 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 ...
-2
votes
2answers
580 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
votes
1answer
322 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 ...
0
votes
1answer
161 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 ...
1
vote
1answer
121 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 ...
0
votes
1answer
32 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
votes
1answer
91 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)....
1
vote
1answer
4k 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 ...
0
votes
2answers
499 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 ...
1
vote
1answer
189 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 ...
0
votes
0answers
32 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 ...
2
votes
0answers
82 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 ...
0
votes
2answers
56 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?
-1
votes
1answer
191 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 ...
-1
votes
3answers
115 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 ...
-1
votes
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 ...
1
vote
1answer
80 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 ...
0
votes
1answer
42 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 ...
-1
votes
1answer
29 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 ...
4
votes
2answers
1k 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 ...
1
vote
0answers
99 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 /...
1
vote
2answers
219 views

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

One mole of hydrated copper(II) sulfate, $\ce{CuSO4 . 5 H2O},$ is dissolved in water. How many moles of ions does the solution contain? 1) 1 2) 2 3) 6 4) 7 The correct answer is 2. ...
1
vote
3answers
116 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?
5
votes
1answer
2k 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 ...
1
vote
2answers
838 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 ...
2
votes
1answer
3k 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: $2\frac{k_1}{k_2}\ce{[NO2]}^2$ $2k_1\ce{[NO2]}^2-2k_2\ce{[N2O4]}$ ...
3
votes
1answer
773 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 ...
0
votes
2answers
187 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 ...
0
votes
1answer
358 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 $K_a = 8.4 \times 10^{-4}$. ...
-1
votes
1answer
3k 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 ...
-1
votes
2answers
338 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 ...
1
vote
0answers
197 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 ...
1
vote
1answer
75 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^{-}}\ \ \...
1
vote
0answers
106 views

What are the optimal conditions for the complete acid hydrolysis (using HCl) of potato starch? [closed]

I'm hoping someone can provide the specifics on the optimal conditions required for the complete acid hydrolysis (using $\ce{HCl}$) of potato starch? I will be using an autoclave (~$\pu{15 psi}$ @ $\...
1
vote
1answer
502 views

Equilibrium change in sealed container

Question: Decreasing the product's concentration seemed to follow the logic of Le Chatelier's principle, so a decrease in volume will force the reaction to the left to increase the pressure (...
1
vote
2answers
3k views

How to calculate the molarity of a gas?

If I have $X$ moles of a gas and I put them in a container at constant volume $V$, will the molarity of the gas then be $X/V$?
1
vote
2answers
365 views

Calculation of molarity using dilution equation [closed]

Using the formula $C_1V_1 = C_2V_2$ I am supposed to calculate the molarity of dilutions. The original solution is $\pu{0.100 M}$ at $\pu{10 mL}$. I diluted it by mixing a $\pu{7.50 mL}$ stock ...
-4
votes
1answer
475 views

Acetic acid in vinegar [closed]

How do I calculate the number of moles of acetic acid present in 25 mL of a 10% vinegar solution?
1
vote
0answers
54 views

Is is possible to Generate ~1ppm Copper in Solution from Elemental Copper? [closed]

I am designing a hydroponic system and need to control algae. Copper is a known algaecide and lettuce actually needs some copper to grow well. I had read stories about people using copper pennies in ...
3
votes
1answer
69 views

Two different methods to express the equilibrium constant give different results

$\pu{2.0M}$ of $\ce{I2}$ and $\pu{2.0M}$ of $\ce{Br2}$ are initially present in a reaction mixture. Calculate the equilibrium concentration of $[\ce{I2}]$ , $[\ce{Br2}]$ and $[\ce{IBr}]$ at $\pu{425K}$...
1
vote
1answer
173 views

Voltaic cell and Nernst equation

It is given voltaic cell $\ce{Cu}|\ce{CuSO4}(\pu{10^-3 M})||\ce{CH3COONa}(10^{-2})|\ce{Pt}(\ce{H2})(\pu{1 atm})$. Find the potential at $\pu{50^\circ C}$. Given $K_\mathrm{a}$ for $H= 1.8 \times ...
0
votes
1answer
321 views

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 ...
-2
votes
1answer
140 views

Using Beers Law and the volume/concentration/moles triangle, but unsure of how to proceed?

pH= 8 Absorbance = 0.997 Concentration mol/l = 6.01E-05 In this experiment I used Beer's law to convert absorbance to concentration with a known extinction coefficient (16.6*10^3) - so 0.997/16600 = ...
3
votes
2answers
276 views

Is it possible to calculate the concentration percentage using chromatography paper?

I'm trying to calculate the concentrations of specific compounds using paper chromatography. Would I be able to calculate a rough estimate by comparing the size of each concentrated spot? If not is ...
1
vote
0answers
37 views

Colorimetry at home?

Is there a reasonably priced option for colorimetry at home? Is this even a good option to accomplish my goal? I'd like to roughly determine the concentration of a chemical in an ethanol extract from ...