Passage III

Gas effusion occurs when a gas moves through a tiny opening into a region of lower pressure. The rate in milliliters per second (mL/sec) is measured using the apparatus in Figure 1.

A 25 mL gas sample in a syringe freely escapes into a flask. The molecular mass, in a.m.u. (atomic mass units), for seven gases and the time required to completely effuse are recorded in Table 1. The densities (mass/volume) in grams per liter (g/L) and average molecular speed (average distance traveled by a molecule per second) in meters per second (m/sec) are also given.

Figure 2 shows a graph of the effusion rate versus the molecular mass of the gases.

17. A 25 mL sample of CO2 gas is allowed to effuse in an apparatus like that in Figure 1. Given the information in Table 1, what percentage of the original number of CO2 gas molecules will remain in the syringe after 11.25 sec of effusion?

Answer and Explanation

Your Answer is

Correct Answer is C

Explanation

Query table 1 and find that the time taken for 25 ml of CO2 to seep out is 22.5 seconds, half of 11.25 seconds, so after 11.25 seconds, half of the gas should still be in the syringe, so choose C