Decays per second, finding mass

[ronpaulkid]

Homework Statement

The activity of a sample of (35/16)Sulfur with a t(1/2) of (7.55*10^6 s) is 3.52*10^5 decays per second.

What is the mass of the sample?

Homework Equations

N=Noe^-lambda*t
lambda=.693/(t1/2)
No/DeltaT=lambda*N

The Attempt at a Solution

My attempt was to use the decays per second given in the equation and divide by lambda which is calculated from (.693/(7.55*10^6s). This will give you an answer N. From there I divided by avogadros number to find moles and then multiplied by the molar mass (35g/mol) to find grams. Didn't work.

 

[phyzguy]

This should work. What answer did you get and what do you think is the right answer?