# Ionic concentration / number of ions

1. Jul 31, 2008

### 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.

2. Jul 31, 2008

### Staff: Mentor

What is mole definition?

3. Jul 31, 2008

### somasimple

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

Consider I'm stupid.

4. Jul 31, 2008

### Staff: Mentor

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?

5. Jul 31, 2008

### somasimple

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

(15/1000)*6.02x10E23

6. Jul 31, 2008

### Staff: Mentor

Wasn't that hard

7. Jul 31, 2008

### somasimple

Sure but I'm so lazy...

8. Jul 31, 2008

### somasimple

9. Jul 31, 2008

### Staff: Mentor

M usually stands for mol/liter.

10. May 20, 2009

### somasimple

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

11. May 20, 2009

### somasimple

No matter, I found the response:

Last edited: May 20, 2009