What exactly is an ion and how do I count them? Calculating number of ions in the following 400mL of .10M FeCl3.
I get... .10M x .4L = 0.04 x 4 ions???= 0.08 ions?
Do I need to use Avogadro's number in the equation?

Question

What exactly is an ion and how do I count them? Calculating number of ions in the following 400mL of .10M FeCl3.
I get... .10M  x .4L = 0.04 x 4 ions???= 0.08 ions?
Do I need to use Avogadro's number in the equation?

aaronq · Answer

0.10M  x .4L = 0.04 $\color{red}{moles}$

moles (n) and atoms/ions/molecules (N) are related by avogadros number $N_A$ by:

$n=\dfrac{N}{N_A}$

you should also take into account the dissociation of $FeCl_3$ into ions.

anonymous · Answer

Chemistry is my most difficult subject. Sorry for being slow but I learn best when working the problem through. So how do I solve for the number of ions?
0.04 x ??? Avogadro's number then what? Some other help sites I've looked at said that the number of ions is basically the number of things you have. For example FeCl3, one ion of Fe and 3 ions of Cl, is this incorrect?

aaronq · Answer

thats right. There are 4 ions in $FeCl_3$

 0.04 moles * $N_A$* 4 =  # of ions

anonymous · Answer

What about something like sucrose? It is not ionic So it doesn't have any ions, right?

aaronq · Answer

nope. but they could ask you how many molecules there are.. and yeah since it doesn't dissociate (break apart) you'd simply multiple the moles by $N_A$.

anonymous · Answer

You're awesome. Thanks for the help!

aaronq · Answer

thanks. no problem !