7 Ca0 + 16 HClVIIO4 7 CaII(ClVIIO4)2 + Cl20 + 8 H2O

This is an oxidation-reduction (redox) reaction:

2 ClVII + 14 e- 2 Cl0 (reduction)

7 Ca0 - 14 e- 7 CaII (oxidation)

Change the oxidation states