NH3 will take approximately 5.88 seconds to effuse.
To calculate how long NH3 will take to effuse, we can use the formula:
Effusion rate of X = (Molar mass of Y / Molar mass of X)^1/2 * Time for X
Given that He takes 20 sec to effuse, we can substitute the values and solve for NH3:
Effusion rate of NH3 = (Molar mass of He / Molar mass of NH3)^1/2 * Time for He
Let's plug in the values:
Effusion rate of NH3 = (4g/mol / 17g/mol)^1/2 * 20 sec = 5.88 sec
Therefore, NH3 will take approximately 5.88 seconds to effuse.