1. The problem statement, all variables and given/known data The initial concentration of reactant in a first-order reaction is 0.75M. The rate constant for the reaction is 2.75/s. What is the concentration (mol/L) of reactant after 6.5s? 2. Relevant equations -kt=[A]initial/[A]anytime 3. The attempt at a solution -(2.75/s)(6.5s)=[0.75M]/[A]@6.5seconds -17.875/1=0.75M/x; x= -4.20x10^-2; The answer to this problem is not right, but I do not have any idea how to go about it another way. Problem 2. The usefulness of radiocarbon dating is limited to 50,000 years. Show mathematically why this is true. (Hint: Remember half life follows first order kinetics. The half life of C-14 is 5.73 x 10^3 years). Half life formula : t1/2= 0.693/k Common integrate rate law for first order reactions: ln[A]=-kt + ln[A@ initial] 5.73x10^3 = 0.693/k, k = 1.21x10^-4/s How would I use k in my integrated formula to prove that the half life is limited to 50,000 years?