How many moles of ions are released when this sample dissolves in water?

3.55*10^18 formula units of
Ba(OH)2*8H2O

You get three ions for each formula unit.

Number ions:3*3.55E18/6.02E23

To determine the number of moles of ions released when 3.55 * 10^18 formula units of Ba(OH)2*8H2O dissolve in water, we need to break down the compound and identify the different ions it contains.

Ba(OH)2*8H2O consists of the cation Ba^2+ and the anions OH^- and H2O molecules (which will not dissociate in water). Each formula unit of Ba(OH)2*8H2O releases two OH^- ions.

First, let's calculate the number of moles of Ba(OH)2*8H2O:
Number of formula units = 3.55 * 10^18

To convert formula units to moles, we need to know the Avogadro's number, which is 6.022 * 10^23 formula units/mole.

moles of Ba(OH)2*8H2O = number of formula units / Avogadro's number
= 3.55 * 10^18 / (6.022 * 10^23)
≈ 5.90 * 10^-6 moles

Since each formula unit of Ba(OH)2*8H2O releases two OH^- ions, we can multiply the number of moles by 2 to find the total number of moles of OH^- ions released.

moles of OH^- ions = 2 * moles of Ba(OH)2*8H2O
= 2 * 5.90 * 10^-6
≈ 1.18 * 10^-5 moles

Therefore, when 3.55 * 10^18 formula units of Ba(OH)2*8H2O dissolve in water, approximately 1.18 * 10^-5 moles of OH^- ions will be released.