(1) The solid of carbon dioxide is called dry ice, which can be used for artificial rainfall and stage clouds, and can also be used as a refrigerant; So the answer is: carbon dioxide

(2) The role of nitrogen is to make nitrogen fertilizer, nitrogen can be used for food packaging bags to prevent corrosion, and light bulbs can be used as protective gas, so the answer is N 2.

(3) Hydrated lime can be used to improve acid soil and also can be used as building materials, so the answer is: Ca(OH) 2.

(4) One of the main ingredients of baking powder for baking cakes is baking soda, namely sodium bicarbonate, so the answer is: NaHCO 3.