Nitrogen-13 emits beta radiation and decays to carbon-13 with a half life of 10 min. Assume a starting mass of 4.00 g of nitrogen -13. How much would remain
after 30 min.?*

Pretty sure it's d. heterogeneous is separated by physical properties. 

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.

Deposition  is  change of state has the wrong energy change listed 

Ans(15) minutes;