Physical property of gas:
There are a lot, here are some examples:
=> Air
=> Oxygen
=> Carbon dioxide
=> Flourine
=> Phosphine
=> Argon
=> Carbon monoxide
This examples are all gases and each of these gases has its own physical property. The only thing that they makes them the same are that, they are gas with lesser molecules. Usually gas density is lesser compare to the solid or liquid and most gases has undefined melting point.
Explanation:
It is known that 1 gram contains 1000 milligrams. And, mathematically we can represent it as follows.
or 
So, when we have to convert grams into milligrams then we simply multiply the digit with 1000. And, if we have to convert a digit from milligrams to grams then we simply divide it by 1000.
The general equation for radioactive decay is;
N = N₀e^(-λt)
x - decay constant (λ) - rate of decay
t- time
N - amount remaining after t days , since we are calculating the half life, amount of time it takes for the substance to to be half its original value, its N₀/2
N₀ - amount initially present
substituting the values
N₀/2 = N₀e^(-0.081t)
0.5 = e^(-0.081t)
ln (0.5) = -0.081t
-0.693 = -0.081t
t = 0.693 / 0.081
= 8.55
half life of substance is 8.55 days
It’s Benzene, I do believe :) hope this helped, good luck!