2) If it takes 24 seconds from the time of concentrated ammonia is opened on demonstration desk until student in front now can smell ammonia, how long will it take from time a little Hydrogen sulphide escapes from the same place until students in the front row can smell Hydrogen sulphide. Given (N=14.0, H=1.0, S=32.0)
Solution
Step I
from Graham's law

Step II
calculate molecular mass by adding atomic masses
i) Ammonia (NH₃); N=14.0;
        

ii) Hydrogen Sulphide H₂S;