Which of the following is a radioisotope used to date rock formations older than 50,000 years?
a. carbon-14.
b. uranium-235.
c. cobalt-69.
d. carbon-12.

Achemist at a pharmaceutical company is measuring equilibrium constants for reactions in which drug candidate molecules bind to a protein involved in cancer. the drug molecules bind the protein in a 1: 1 ratio to form a drug-protein complex. the protein concentration in aqueous solution at 25 ˚c is 1.74 x10-6 m . drug a is introduced into the protein solution at an initial concentration of 2.00 x10-6m. drug b is introduced into a separate, identical protein solution at an initial concentration of 2.00 x10-6m. at equilibrium, the drug a-protein solution has an a-protein complex concentration of 1.00 x10-6m, and the drug b solution has a b-protein complex concentration of 1.40 x10-6m. a. calculate the kc value for the a-protein binding reaction. b. calculate the kc value for the b-protein binding reaction. c. assuming that the drug that binds more strongly will be more effective, which drug is the better choice for further research?