College Chemistry
posted by Jude .
A rock containing 238U and 206Pb was examined to determine its appropriate age. The molar ratio of 206Pb to 238U was 0.1462. Assuming no lead was originally present and that all lead formed remained in the rock. What is the age of the rock in years? The half life of 238U is 4.500*10^9yr

amount remaining= original*e^(693t/halflife)
.1462=1 e^( )
take the ln of each side
ln (.1462)=.693 t/4.5E9
t= 4.5E9 /693 * ln (.1462) That is a long time. 
I tried this but was told the answer was wrong.