1. Which of the following choices demonstrates the law of constant composition? (Slides 2 ‒ 3: Laws on Matter) (a) Nitrogen and oxygen are both found in nature as diatomic molecules. (b) When 20.0 g of nitrogen and 32.0 g of oxygen are combined and allowed to react in two separate experiments, both times the product isolated from reaction contains 14.0 g of nitrogen and 32.0 g of oxygen. (c) Nitrogen and oxygen gases are mixed to produce a sample consisting of 20.0 g of nitrogen and 32.0 g of oxygen. (d) When 14.0 g of nitrogen and 32.0 g of oxygen are mixed and react, there is no measurable change in mass during the reaction. (e) Nitrogen and oxygen are gases found in air, nitrogen is approximately 79% of air and oxygen is approximately 21%.

(b) When 20.0 g of nitrogen and 32.0 g of oxygen are combined and allowed to react in two separate experiments, both times the product isolated from reaction contains 14.0 g of nitrogen and 32.0 g of oxygen.

Explanation:

The law of definite proportion states that a gen chemical compound always contains its constituent elements in a fixed ratio by mass, independent on the method of preparation.

The molar mass of Nitrogen and Oxygen would always remain the same, allowing for exact reactant masses (or mole ratio) irrespective of the given amount of sample.

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

idk what the question is about