A sample initially contains 150.0 mg of radon-222. After 11.4 days, the sample contains 18.75 mg of radon-222. Calculate the half life of radon-222.

If 10.0 ml of the solution on the right are withdrawn from the 100 ml beaker and diluted again in a similar manner, what is the new concentration? m nacl

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

As changes in energy levels of electrons increase, the frequencies of atomic line spectra they emit