Please note that the reactions provided are chemical equations showing the transformation of compounds into other compounds. The arrows indicate the direction of the reaction.

P2O5 -> x -> K3PO4 -> FePO4 (Phosphorus Pentoxide -> Intermediate x -> Potassium Phosphate -> Iron(II) Phosphate)Si-SiO2 -> NaSiO3 -> H2SiO3 -> SiO2 (Silicon - Silicon Dioxide -> Sodium Metasilicate -> Metasilicic Acid -> Silicon Dioxide)CuO -> CuCl2 -> Cu$OH$2 -> CuSO4 -> Cu (Copper(II) Oxide -> Copper(II) Chloride -> Copper(II) Hydroxide -> Copper(II) Sulfate -> Copper)FeCO3 -> FeO -> FeCl2 -> FeS -> FeSO4 (Iron(II) Carbonate -> Iron(II) Oxide -> Iron(II) Chloride -> Iron(II) Sulfide -> Iron(II) Sulfate)P2O5 -> H3PO4 -> Na3PO4 -> Ca3$PO4$2 -> H3PO4 (Phosphorus Pentoxide -> Phosphoric Acid -> Sodium Phosphate -> Calcium Phosphate -> Phosphoric Acid)P2O5 -> x -> K3PO4 -> Ca3$PO4$2 (Phosphorus Pentoxide -> Intermediate x -> Potassium Phosphate -> Calcium Phosphate)H2S -> S -> x -> Na2SO3 (Hydrogen Sulfide -> Sulfur -> Intermediate x -> Sodium Sulfite)CaO -> x + Na2CO3 -> CaCO3 -> CO2 (Calcium Oxide -> Intermediate x + Sodium Carbonate -> Calcium Carbonate -> Carbon Dioxide)MgSO4 -> x -> MgO -> Mg$NO3$2 (Magnesium Sulfate -> Intermediate x -> Magnesium Oxide -> Magnesium Nitrate)CuCl2 -> x -> CuO -> CuSO4 (Copper(II) Chloride -> Intermediate x -> Copper(II) Oxide -> Copper(II) Sulfate)