The half-life of any substance is the amount of time taken for half of the original quantity of the substance present to decay. The half-life of a radioactive substance is characteristic to itself, and it may be millions of years long or it may be just a few seconds.
In order to determine the half-life of a substance, we simply use:
t(1/2) = ln(2) / λ
Where λ is the decay constant for that specific isotope.
Answer:
32(molecular mass has no unit )
Explanation:
(16)(o2)
16×2
=32
Answer:
Surface runoff and condensation
Explanation:
Let's define each of the given processes in order to understand them better:
- evaporation is a process in which liquid phase transforms into a gas phase;
- precipitation is a process in which we produce a solid phase, usually this is the case when we precipitate a salt out of a solution, analogy of precipitation for water would be transformation from a liquid to a solid phase, such as freezing;
- surface runoff is a process in which water flows over the surface of a land without any change in its phase;
- condensation is a process in which a gas transforms into a liquid.
All in all, notice that surface runoff keeps water in its liquid state, while all the other three options consider phase change. The only phase change of interest is condensation: we produce liquid water from water vapor and then we can analyze its movement in the liquid state.
You start by diving each quantity given by the atomic wight of each element:
Phosphorus (P) 
Hydrogen (H) 
Then you divide by the lowest number:
for phosphorus
for hydrogen
So the empirical formula will be:
