Question

2. One student takes 3.0 grams of unknown pure substance #1 and de- composes it to its constituent elements, nitrogen and oxygen. He finds that it is composed of 0.91 grams of nitrogen with the remainder being oxygen. A second student takes 10.5 grams of unknown pure substance #2 and decomposes it to its elements in the same fashion as the first student. She finds that unknown substance #2 consists of 3.2 grams of nitrogen with the remainder being oxygen. What is the mass percent of nitrogen and oxygen in each of the two unknown samples? What is the relationship between the different unknowns according to Dalton’s Atomic Theory?

Answer 1

Answer:

Substance 1;

Nitrogen = 30.33%

Oxygen = 69.67%

Substance 2;

Nitrogen = 30.47%

Oxygen = 69.52%

The two substances contain the same atoms of the elements nitrogen and oxygen in about the same ratio.

Explanation:

Percentage of nitrogen in substance 1

0.91/3 × 100 = 30.33%

Percentage of oxygen in substance 1

(3-0.91/3) × 100 = 69.67%

Percentage of nitrogen in substance 2

3.2/10.5 × 100 = 30.47%

Percentage of oxygen in substance 2

(10.5 -3.2/10.5) × 100 = 69.52%