Ionic concentration / number of ions

[somasimple]

Hi all,

We use often concentrations in chemical/biological experiments.
It is expressed usually in mili/µ mole/cm3 or mm3

Is there a way to know the number of ions contained in a volume?
Is there a way to know the number of ions (or density) on a surface knowing the concentration?

Sorry for these basic questions.

 

[Borek]

What is mole definition?

 

[somasimple]

Mole: a chemical mass unit, defined to be 6.022 x 10E23 molecules, atoms, or some other unit.

Consider I'm stupid.

 

[Borek]

Mole: a chemical mass unit, defined to be 6.022 x 10E23 molecules, atoms, or some other unit.

Not a mass unit, quantity unit. But you are right - 6.02x10²³ of elements. Just an overgrown dozen it is.

Do you know how to calculate number of moles of substance given volume of sample and concentration?

 

[somasimple]

I suppose.
If the concentration is 15 mMole then the number of molecules contained per unit of volume is:

(15/1000)*6.02x10E23

 

[Borek]

Wasn't that hard

 

[somasimple]

Sure but I'm so lazy...

 

[somasimple]

What is the volume unit on this page?
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=.0Doz_14FBoKlEE7VO_HAyJwxnZMXWZZQAN0H9

 

[Borek]

M usually stands for mol/liter.

 

[somasimple]

Many salt are solvated in water.
How many water molecules are in a liter?

 

[somasimple]

No matter, I found the response:

1 liter of water has mass about 1000 grams/liter.
Molecular mass of water=18
so No. of moles in 1liter = 1000/18= 55.55 moles
this multiplied by Avogadro's number: 6.022*10²³
will give number of water molecules in 1 liter as:
55.55*6.022*10²³ ~= 334.52*10²³