The graph below shows the decay of a radioactive isotope. what is the half-life of the isotope?
a. 15 seconds
b. 25 seconds
c. 40 seconds
d. 200 seconds
the graph is in an attachment. : )

What amount of heat is exchanged when 106.2 grams of substance y goes from a liquid at 35 degrees celsius to a solid at the same temperature? melting point of substance y = 35 degrees c; δhvaporization = 3.67 j/mol; δhfusion = 3.30 j/mol. mwsubstance y = 28.22 g/mol. −12.4 j −3.51 x 102 j 1.24 x 101 j 351 j