Answer: It will produce 40 chloride ions
Explanation: When in water, Calcium chloride separate in ions, as the following chemical equation:
CaCl₂ + H₂O ⇒

According to the equation, 1 calcium chloride results in 2 chloride ions, so if there are 20 units of the chemical compound, there will be 2 times as much Chlorine ions, i.e., 40 units of chlorine ions.