A)
Each mole of Rb₃PO₄ will release:
3 moles of Rb⁺
1 mole of PO₄⁻³
So a total of 4 moles of ions are released per mole.
If there are 0.5 moles, 2 moles of ions will be released.
B)
Each mole of Cr₂(SO₄)₃ will release:
2 moles of Cr⁺³
3 moles of SO₄⁻²
So a total of 5 moles of ions are released per mole.
When there are 0.5 moles, 2.5 moles of ions will be released.