If hcl were added to a solution containing lead(ii) ions, sodium ions, nickel(ii) ions, and potassium ions, which ions would precipitate? (select all that lead ions. nickel ions. potassium ions. sodium ions. none of them

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)