Answer:
18.06 × 10²³ molecules
Explanation:
Add the two amounts of molecules together.
6.02 × 10²³ + 12.04 × 10²³ = 18.06 × 10²³
You will have 18.06 × 10²³ molecules in the vessel when the reaction is complete. This is because of the Law of Conservation of Mass. Mass is neither created nor destroyed in chemical reactions. You will have the exact number of molecules in the reaction vessel as you did in the beginning. The types of molecules may change, but the number will stay the same.
The group 7A elements are called Halogens.
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Example :

If you use the subscript (aq) (=aquaris) , this means that the substance is in a solution.
Subscripts:
-aq-this means that the substance is in a solution
-s-this means that the substance is a solid(or precipitate)
-l-this means that the substance is a liquid
-g-this means that the subtance is a gas