If 6.02*10^23 molecules of ammonia react with 12.04*10^23 molecules of hydrogen chloride, how many molecules are in the reaction vessel when the reaction is complete

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.

- decrease the number of plants and animals living in the water.