See detailed explanation.
a. In this case, considering sodium chloride, sodium a chlorine a typical chemical reaction could be used in order to stand out their differences. For instance, when mixed with water sodium chloride just dissolves in it, sodium readily reacts yielding sodium hydroxide via a very exothermic chemical reaction which also fires on sodium and hydrogen gas s given off:
Moreover, chlorine reacts with water to yield hypochlorous acid and hydrochloric acid in a very slow equilibrium reaction:
b. In this case, regarding nitrogen dioxide, nitrogen and oxygen, it is widely known that nitrogen dioxide is a red-brown gas which is also toxic whereas both nitrogen and oxygen are colorless.
i wish i could but this one is weird give me abc and i can solve it.