# Ionic concentration / number of ions

by somasimple
Tags: ion, volume
 PF Gold P: 716 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.
 Admin P: 23,578 What is mole definition?
 PF Gold P: 716 Mole: a chemical mass unit, defined to be 6.022 x 10E23 molecules, atoms, or some other unit. Consider I'm stupid.
P: 23,578
Ionic concentration / number of ions

 Quote by somasimple 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?
 PF Gold P: 716 I suppose. If the concentration is 15 mMole then the number of molecules contained per unit of volume is: (15/1000)*6.02x10E23
 Admin P: 23,578 Wasn't that hard
 PF Gold P: 716 Sure but I'm so lazy...
 PF Gold P: 716 What is the volume unit on this page? http://www.ncbi.nlm.nih.gov/books/bv...xnZMXWZZQAN0H9
 Admin P: 23,578 M usually stands for mol/liter.
 PF Gold P: 716 Many salt are solvated in water. How many water molecules are in a liter?
PF Gold
P: 716
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

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