The density of iron is 7.87 g/mL.  Some iron was placed into…

The density of iron is 7.87 g/mL.  Some iron was placed into a graduated cylinder containing 25.0 mL of water.  The water level rose to 37.9 mL.  Determine the mass of zinc knowing that the equation for density is d = m/V.  Please include units and the correct number of significant figures in your answer (7 points).

A radioactive nucleus Pb-208 undergoes an alpha decay. (a) w…

A radioactive nucleus Pb-208 undergoes an alpha decay. (a) write the complete nuclear reaction (b) if 420g of Pb-208 is initially present, how much will be left after 3 half-lives? (c) what is the mass percentage remaining after the 3 half-lives? Show work for full credit.