Question

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 apply.)
lead ions
nickel ions
potassium ions
sodium ions
none of them

Answer 1

To predict the solubility of the compounds you should base on solubility tables.

I used one from wikipedia. If you google "solubility table" you will find this table as first option.

There I found that nickel, potassium and sodium chlorides are very soluble with solubilities of two digits. While lead clhoride has a solubility close to 1 g per 100 g of water. Then lead is the ion that will precipitate with certainty.