19. cerium is the most abundant rare earth metal. pure cerium ignites when
scratched by even a soft object. it has four known isotopes: "ce (atomic mass
= 135.907 amu), ce (atomic mass = 137.905 amu), 4°сe (atomic mass =
139.905 amu), and "ce (atomic mass = 141.909 amu). ce-140 and ce-142 are
fairly abundant. which is the more abundant isotope?

Agroup of students is studying convection current. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other is in an area with warm air. after 10 minutes, the balloon are released from a height of 1 meter. which of the following to the students most likely observe? a) the warm balloon expands and rises. the cold balloon shrinks and sinks b) the balloon both rise. the cold balloon is larger than the warm balloon c) the cold balloon expands and rises. the warm balloon shrinks and sinks d) the balloon rise at the same rate. both balloons are the same size

Show how to convert the temperature 84.7° c to kelvin. include all steps and label the final answer

Which of the following is true regarding chemical and nuclear reactions?