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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10
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4answers
6k views

Why do solutions become saturated?

Why can a solvent dissolve only a particular amount of solute? If we add more solute to the solution, the number of solute particles in contact with water increases. So rate of dissolution should ...
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1answer
2k views

Photosynthetic rate calculation

What are the steps in calculating the photosynthetic rate ($\mu\text{mole}\ce{O2}/$ $\text{m}^2 / \text{min}$) for a leaf that has an area of $0.0025 \text{m}^2$ and a $\ce{O2}$ evolution rate of $...
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4answers
419 views

How do I create a concentrated solution of singlet oxygen (in the dark)?

Without appealing to reactions that require photons / light, how do chemists achieve a very high concentration of continually produced, though quite short lived, singlet oxygen in aqueous solution (i....
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2answers
1k views

Calculating the molartity of DNA in a cell

In the following questions use a value of 3 for $\pi$, $6 \times 10^{23}$ for Avogadro’s number and 660 for the molecular weight of 1 bp of DNA. The volume of a sphere of radius r is $4/3\,πr^3$. ...
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1answer
8k views

What is an equivalent?

I want to know what is an equivalent and how is it different from equivalent mass. How to calculate and why is it used in chemistry for knowing concentration?
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1answer
253 views

Molarity exercises [closed]

Can anyone direct me to a good book with lots of molarity exercises, i really want to practice this and would like to find as many types of exercises involving molarity. I of course did google this ...
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1answer
8k views

I need to make a solution with a specific concentration. How do i find the mass?

I have to make a 250 mL solution of $\ce{Mg(NO3)2}$, the concentration of the solution has to be 0.3 mol/L. How can I find out the mass of how much $\ce{Mg(NO3)2}$ I need to use?
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1answer
2k views

$\beta$-mercaptoethanol molarity

I'm writing up a practical and $\beta$-mercaptoethanol was used, with no concentration given. I've found I don't need the BME molarity since I'm giving percentage (v/v) concentration, however I'm ...
8
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1answer
207 views

How should I modify my molecular dynamics simulation so that known chemical reactions can be modelled?

I have written some molecular dynamics code that I want to use to model known chemical reactions. By known I mean that it has been observed in a lab that $\ce{A +B->C}$. I am not interested in ...
1
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1answer
11k views

Finding molar mass of an unknown acid

"In the titration of a solid acid, an endpoint is reached after 22.0mL of 0.120 M $\ce{NaOH}$ has been added. Assuming that each acid particle contains two acidic hydrogens and both are ...
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1answer
170 views

What does this scale mean?

$$\log_{10}~\mathrm{pg}/\mathrm{ml}$$ I do not understand the scale. How do I convert this to a standard concentration (without the logs)?
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3answers
2k views

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 ...
14
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1answer
341 views

Why do some solutions eventually stop boiling and start “popping” as they get more concentrated?

A very long time ago I performed an experiment in my kitchen, part of which was to remove all water from a solution. Unfortunately I don't remember what was in it, but the point is that as the ...
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0answers
428 views

Basic chemistry equation with ammonia [closed]

A table in the book 'Chemistry NCEA Level 1' has 4 headings, the first of which is 'Volume (mL) ammonia solution provided (conc 2 g L-1)' Could someone please provide a comprehensive explanation of ...
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2answers
130k views

What do the different grades of chemicals mean?

When purchasing chemicals from Sigma, Fisher, or wherever, there are often -grade's attached to their description like reagent-grade, technical-grade, analytical-grade, or more niche-sounding biotech-...