This is a series of chemical reactions involving strontium (Sr) and phosphoric acid (H3PO4):

Sr + O2 -> SrO (formation of strontium oxide)SrO + H2O -> Sr(OH)2 (formation of strontium hydroxide)Sr(OH)2 + H3PO4 -> Sr(H2PO4)2 + H2O (formation of strontium dihydrogen phosphate and water)

Overall reaction:
Sr + H3PO4 -> Sr(H2PO4)2 + H2O