Final answer:
When 40.0 grams of ammonium nitrate explode and form 14.0 grams of nitrogen and 8.0 grams of oxygen, 18.0 grams of water form as a result, as deduced from the law of conservation of mass.
Step-by-step explanation:
To determine how many grams of water form when 40.0 grams of ammonium nitrate explode, we can apply the law of conservation of mass, which states that mass is neither created nor destroyed in a chemical reaction.
The total mass of products formed from the explosion must equal the starting mass of the ammonium nitrate, which is 40.0 grams.
The question already provides the mass of nitrogen and oxygen formed: 14.0 grams of nitrogen and 8.0 grams of oxygen.
The mass of water can be calculated by subtracting the combined mass of nitrogen and oxygen from the total starting mass:
Mass of water = Total starting mass - (Mass of nitrogen + Mass of oxygen)
Mass of water = 40.0 g - (14.0 g + 8.0 g)
= 18.0 g
Therefore, 18.0 grams of water are formed from the explosion of 40.0 grams of ammonium nitrate.