(2) U-238 is the radioisotope used in dating geological formations. Uranium-238 has a half-life of 4.46 billion years, which makes it suitable to date such old formations.
The other options do not have such long durabilities and half-lives.
It is 50. The answer is 50. 10x5=50 50x1=50
Use M1V1 = M2V2 to solve
3(V1) = 2.8 * 1.6
3(V1) = 4.48
V1 = 1.493 L of stock solution
1. combustion
2. succession
3. condensation
4. precipitation
5. pioneer species
6. decomposition
7. evaporation
8. nitrogen fixation