1. The problem statement, all variables and given/known data Thorium (with half-life T1/2 = 1.913 yr. and atomic mass 228.028715 u) undergoes alpha decay and produces radium (atomic mass 224.020186 u) as a daughter nucleus. (Assume the alpha particle has atomic mass 4.002603 u.) (a) What is the decay constant of thorium? (Note that the answer must be in units of hrs-1.) Answer: 4.136E-5 hrs-1 The energy released from the decay of 10 g of thorium is used to heat 3.8 kg of water (assume all the energy released goes into the water). (c) What is the change in temperature of the water after 1 hr.? 2. Relevant equations E=mc2 N0= Mtotal/Mparticle N=N0e^-λt Q=mcT 3. The attempt at a solution N0= Mtotal/Mparticle N0=[(0.01kg)]/[(228.0287u)(1.66E-27kg)] N0=2.64E22 atoms N=N0e^-λt N=(2.64E22 atoms)e^-(4.136E-5 hrs-1)(1hr) N=2.642E22 atoms mi=228.028715u mf=224.020186u + 4.002603u mf=228.022789u m=mf-mi m=228.022789u - 228.028715u m=0.005926u E=mc2 E=(0.005926u)[(931.5Mev/c2)/u]c2 E=5.52Mev (5.52Mev)(1.602E-13J/Mev) = 8.843E-13 J (8.843E-13J)(2.642E22 atoms)=2.336E10J Q=mcT 2.336E10J=(3.8kg)(4186 J/kg-K)(T) T=1468755.878 K = 1468482.878 C Can someone help me catch my mistake? I'm not sure what I did wrong. Thank you.