Answer
a) $2\ Na^+, CO_3^{2-}$
b) $Cu^{2+}, SO_4^{2-}$
c) Insoluble.
d) $Ba^{2+}, 2\ Br^{-}$
Work Step by Step
a) $2\ Na^+, CO_3^{2-}$
Sodium salts are almost always soluble.
b) $Cu^{2+}, SO_4^{2-}$
Sulfates are usually soluble, copper (||)'s is not an exception.
c) Insoluble.
Sulfides are usually insoluble, and Nickel (||)'s is not an exception.
d) $Ba^{2+}, 2\ Br^{-}$
Bromides are usually soluble, and barium's is not an exception.
