Chemistry 2005 JAMB Past Questions - Question 20: 25cm² of a mixture of noble gases was obtained from air after the removal of other constituents. What was the original volume of air?

Correct Answer

A

Explanation

Nobel gas is about 1% of the air
To determine the original volume of air, we need more information about the composition of air and the specific noble gases present. However, if we make certain assumptions, we can estimate the original volume.

The Earth's atmosphere is composed mainly of nitrogen (about 78%) and oxygen (about 21%), with trace amounts of other gases, including noble gases like argon (about 0.93%). Assuming the mixture of noble gases obtained from air contains only argon, we can proceed with this estimation.

Let's assume the original volume of air (before removal of other constituents) is \(V\). The volume of argon in the air would then be \(0.0093 \times V\) (since argon makes up about 0.93% of air).

If 25 cm² of a mixture of noble gases was obtained, we have:

\[ 0.0093 \times V = 25 \, \text{cm}^3 \]

Now, we can solve for \(V\):

\[ V = \frac{25}{0.0093} \]

\[ V \approx 2688.17 \, \text{cm}^3 \]

So, the estimated original volume of air is approximately 2688.17 cm³. Keep in mind that this is a rough estimation based on the assumptions made about the composition of air, and actual atmospheric composition may vary.