Answer: No reaction occurs
Explanation:.
Spectator ions are defined as the ions which does not get involved in a chemical equation or they are ions which are found on both the sides of the chemical reaction present in ionic form.
The given chemical equation is:

The complete ionic equation is;

The ions which are present on both the sides of the equation are are not involved in net ionic equation.
Hence, there is no net reaction.
Answer: 20 mg Te-99 remains after 12 hours.
Explanation: N(t) = N(0)*(1/2)^(t/t1/2)
N(t) = (80 mg)*(0.5)^(12/6)
N(t) = 20 mg remains after 12 hours
The hydroxide (OH) in the metallic hydroxide will react with the hydrogen in an acid to form H2O. The remaining ions will combine to form a salt. Therefore a metal hydroxide and an acid will form a salt + water.