How many moles of Na+ ions are in 20 mL of 0.40 M Na3PO4?

`Na_3PO_4` will
ionized as follows in an aqueous solution.

`Na_3PO_4 rarr
3Na^++PO_4^(3-)`

As we can see from the balanced equation one `Na_3PO_4` will
give us three `Na^+` moles.

Amount of `Na_3PO_4 = 0.4/1000xx20 =
0.008mol`

 

Mole ratio

`Na_3PO_4:Na^+ =
1:3`

 

Amount of `Na^+` `= 0.008xx3 = 0.024mols`

 

So we have 0.024 moles of `Na^+`
ions.