1. The problem statement, all variables and given/known data Calculate the radioactive concentration (MBq/ml) of a sodium pertechnetate [99mTC] solution with a concentration of 2.0 * 10^-6 g/L. Mr (sodium pertechnetate) = 186 half life of [99mTc) = 6.02 hours Avagadro's constant = 6.02 * 10^23 2. Relevant equations A= lamda N N = mNa/Mr Moles=mass/Rmm C=n/v 3. The attempt at a solution Okay, so the first step would be to work out the decay constant (lamda) from the half life which I can do but, after that I kind of get stuck. Do I need to calculate the activity (A) by using the formula A= lamda N? How do I work out N if I don't have the mass to work out the moles of the compound? And then how does that enable me to work out the concentration using c=n/v without a volume Also, am I going about the question the correct way?