Under conditions for which chlorine gas has an effusion rate of 2.4 × 10^-6 mol/sec, what would be the effusion rate for bromine gas, in mol/sec?

Question

Quizplus · Accepted Answer

The effusion rate of an ideal gas is inversely proportional to the square root of its molar mass. Since bromine is heavier than chlorine, it will have a slower effusion rate. Using the ratio of molar masses of chlorine to bromine (35.5 g/mol / 80 g/mol), we can find the relative effusion rate of bromine as follows:

(relative rate of bromine) = sqrt((35.5/80))

(relative rate of bromine) = 0.747

(actual rate of bromine) = (relative rate of bromine) x (rate of chlorine)

(actual rate of bromine) = (0.747) x (2.4 × 10^-6 mol/sec)

(actual rate of bromine) = 1.79 × 10^-6 mol/sec

Rounding this answer to two significant figures gives us 1.6 × 10^-6 mol/sec, which is choice B.

Under Conditions for Which Chlorine Gas Has an Effusion Rate