?$ (1)\ \text {Ca(OH)}_2+\ \text {H}_2\ \text {SO}_4\xlongequal[\ \ \ \ \ \ ]{}\ \text {CaSO}_4+2\ \text {H}_2\ \text {O}$?
?$ (2) \mathrm{Mg(OH)_2+2HCl\xlongequal[\ \ \ \ \ \ ]{}Mg_Cl_2+2H_2O } $?
?$ (3) 2\ \text {NaOH+H}_2\ \text {SO}_4\xlongequal[\ \ \ \ \ \ ]{}\ \text {Na}_2\ \text {SO}_4+2\ \text {H}_2\ \text {O}$?
