An unknown element consists of two stable isotopes. The first has an atomic mass of 137.9068 amu and a percentage natural abundance of 0.09%. The second has an atomic mass of 138.9061 amu and a percentage natural abundance of 99.91%. What is the atomic mass of the element

16. in a reaction that has reached equilibrium, a. the forward and reverse reactions are occurring at the same rate. b. the reactants and products are in equal concentrations. c. the forward reaction has gone further than the reverse reaction. d. there are equal numbers of atoms on both sides of the equation. e. a, b, and d are correct.