1)
`2K+2H_2 O->2KOH+H_2`
`Ca+2H_2 O->Ca(OH)_2 +H_2`
2)
`Na_2 O+H_2 O->2NaOH`
`CaO+H_2 O ->Ca(OH)_2`
3)
`P_2 O_5 +3H_2 O->2H_3 PO_4`
1.\(2K+2H_2O\xrightarrow[]{}2KOH+H_2\)
\(Ca+H_2O\xrightarrow[]{}CaO+H_2\)
2.\(Na_2O+2H_2O\xrightarrow[]{}2NaOH+H_2\)
\(CaO+H_2O\xrightarrow[]{}Ca\left(OH\right)_2\)
3.\(P_2O_5+3H_2O\xrightarrow[]{}2H_3PO_4\)