A 0.21 M solution of AlF contains 0.21 moles of molecules for each liter of solution. In this problem we have only 65.5 mL (0.0655 L) of solution, so the number of moles is
Ionization of each AlF unit produces one fluoride ion (
Finally, to obtain the actual number of ions, we multiply by Avogadro's number:
or, in the case of
I assume you are referring to an aluminium fluoride,
To determine the number of fluoride ions present in that particular solution, you must first determine how many moles of aluminium fluoride you have.
Molarity is defined as the number of mole of solute, in your case aluminium fluoride, divided by liters of solution. Since you know what the molarity of the
Now, because aluminium fluoride is an ionic compound that's soluble in water, your solution will contain
Notice that you have a
To get the exact number of fluoride ions present in your solution, use the fact that 1 mole of a substance contains exactly
In your case, 1 mole of fluoride ions will contain
Rounded to two sig figs, the number of sig figs given for 0.21 M, the answer will be
First of all, the formula
Molarity means moles/L. So
Convert the volume of the solution from mL to L.
Now multiply the volume of the solution in liters times the molarity.