9. Birds today have bones with 10mg of Ca-50. A bird bone is found with only 1.25mg of Ca-50 in it. If the ½ life of Ca-50 is 4 yrs, how old is the bone?

The reactions of photosynthesis occur in the of plant cell? a.mitochondria. b. lysosomes. c. chloroplasts. d. chlorophyll

Helium decays to form lithium. which equation correctly describes this decay?

When the ionic compound nabr dissolves in water, br– ions are pulled into solution by the attraction between what two particles? a. the na+ and br– ions b. the na+ ion and the negative end of a water molecule c. the br– ion and the positive end of a water molecule d. the br– ion and the negative end of a water molecule