Question

A sealed flask at 20°C contains 1 molecule of carbon dioxide for every 3 atoms of helium. If the total pressure is 800 mmHg, what's the partial pressure of helium?

a) 200 mmHg
b) 400 mmHg
c) 600 mmHg
d) 800 mmHg

Answer 1

The partial pressure of helium in a sealed flask with a 1:3 ratio of CO2 to He and a total pressure of 800 mmHg is calculated using Dalton's Law to be 600 mmHg.

Step-by-step explanation:

The question is about calculating the partial pressure of helium in a mixture of gases according to Dalton's Law of Partial Pressures. Given the ratio of 1 molecule of carbon dioxide (CO2) to every 3 atoms of helium (He), and the total pressure of 800 mmHg, we can determine the partial pressure of helium. Since the quantity of helium is three times that of carbon dioxide, helium will exert three-quarters of the total pressure.

To find the partial pressure of helium (PHe), we use the formula:
PHe = (3/4) × total pressure. Plugging in the values, we get:
PHe = (3/4) × 800 mmHg = 600 mmHg.

Therefore, the partial pressure of helium is 600 mmHg, making the correct answer (c) 600 mmHg.