Lead-202 has a half-life of 53,000 years. How long will it take for 15/16 of a sample of lead-202 to decay?.

Asample of the male sex hormone testosterone, c19h28o2, contains 3.88×10^21 atoms of hydrogen.(a) how many atoms of carbon does it contain? (b) how many molecules of testosterone does it contain? (c) how many moles of testosterone does it contain? (d) what is the mass of this sample in grams?

You are to give ampicillin with a recommended dose of 25mg/kg to a child with a mass of 29kg. if stock on hand is 250mg/capsule how many capsules should be given?

Which element has the lowest electronegativity? calcium(ca) gallium(ga) selenium(se) bromine(br)