40 ml of gas A effuse through the pin hole in 140 seconds. The same volume of CO2 under identical conditions effuse in 110 seconds. Calculate the molecular mass of gas A and predict its identity.

Answer 1

First, we need to calculate the rate of effusion for each gas by comparing the time taken for the same volume of gas to effuse.

Rate of effusion for gas A = Volume of gas A / Time taken for gas A to effuse = 40 ml / 140 seconds = 0.285 ml/s
Rate of effusion for CO2 = Volume of CO2 / Time taken for CO2 to effuse = 40 ml / 110 seconds = 0.364 ml/s

Next, we use Graham's law of effusion to determine the molecular mass of gas A:
Rate of effusion of gas A / Rate of effusion of CO2 = sqrt(Molecular mass of CO2 / Molecular mass of gas A)

0.285 / 0.364 = sqrt (44 / x)
0.783 = sqrt (44 / x)
0.783^2 = 44 / x
0.613 = 44 / x
x = 44 / 0.613
x = 71.7

Therefore, the molecular mass of gas A is approximately 71.7 g/mol. Based on this molecular mass, the gas is most likely iodine (I2) as its molecular mass is approximately 253 g/mol in the elemental state.