Radiometric Dating Problems Lab

NAME ___________________ DATE __________ HOUR ______ Use the general decay curve to answer the following: 1. A fossil log sample was sent to the lab for a radioactive determination. The was used. Of the original 240 grams of 14C only 15 grams of 14C remain. 14 C → 14N radioactive decay How many half lives has this sample been through? _______________ What is the age of the log? _____________________ How many grams of 14N must be in the log? 2. Gneiss was submitted for radioactive analysis. Certain minerals in the gneiss were found to contain 40 K. The 40 K → 40Ar method was used. The results of the analysis found 40K= 20g and 40Ar = 300 g. What is the D/P ratio? ______________ How many half lives has this sample been through? _________ What is the age of the gneiss? ______________ Is there a problem with this answer? Explain _____________________________________________ 3. A sample of basalt was analyzed using the 3H →3He method (one half life= 12.3 years). Results of the granite are 3H = 2g and 3He = 100g. What is the D/P ratio? _____ What is the age of the basalt? _______________________ 4. A sample of gneiss was analyzed using the 235U → 207 Pb method. U = 2g and 207Pb= 12g 235 What is the D/P ratio? _________ What is the age of the gneiss? _____________ 5. A rock sample is analyzed using the 14C → 14N method. If the D/P ratio is 100, how old is the sample? _______________ 6. A sample of granite is analyzed using the 40K → 40 Ar method. Of the original 300 of potassium only 75 grams remain. How many half lives has this granite been through? _______________ How old is this sample? _____________ What geologic era did this granite form in?