Question

Ba+HOH-
Ba+HCl-
Sr+O2-
Ca+Cl2-
Sr+Br2-
2- это внизу двойка 

Answer 1

$Ba+2HOH=Ba(OH)_{2} +H _{2} \ \ Ba+2HCl=BaCl _{2} +H _{2} \ \ 2Sr+O _{2} =2SrO \ \ Ca+Cl _{2} =CaCl _{2}$