The relationship between pressure and solubility of the gas is given by Henry's law as:

where,
is the solubility of the gas.
is proportionality constant i.e. Henry's constant.
is pressure of the gas.
(given)
(given)
Substituting the values,

To convert
to
:
Molar mass of benzene,
= 

Now for converting into
:
Since, 
So,
.
Hence, the solubility of benzene in water at
in
is
.
Answer:
36.92 mg of oxygen required for bio-degradation.
Explanation:

Mass of benzene = 30 mg = 0.03 g (1000 mg = 1 g )
Moles benzene =
According to reaction 5 moles of benzene reacts with 15 moles of oxygen gas.
Then 0.0003846 mol of benzene will react with:
of oxygen gas
Mass of 0.0011538 moles of oxygen gas:
0.0011538 mol × 32 g/mol = 0.03692 g = 36.92 mg
36.92 mg of oxygen required for bio-degradation.
B. The unknown solution had the lower concentration.
Explanation:
Osmosis is a phenomenon in which the molecules of the solvent has a tendency to move through a membrane which is semipermeable from lower concentrated side to the higher concentration side, so that the concentrations on both sides of the membrane must be equal.
So the unknown solution may have lesser concentration than the isotonic solution so that molecules of that solution move from less concentrated side to the more concentrated side, so its level drops.
<span>Raising
the temperature of the reactants increases the reaction between the reactants.
The kinetic energy of the molecules of the reactants collides more frequently
with ach other thereby increasing its reaction. Increasing the concentration of
the reactants increases the reaction rate. Adding a catalyst to the reaction
increases the rate of reaction of a substance. The catalyst hastens the
chemical reaction. </span>
When electrons are filling energy levels, the lowest energy sublevels are occupied first. This is Hund's rule.
Hund's rules state that:
Every orbital in a sublevel has to be singularly occupied before any other orbital is able to be doubly occupied.
All of the electrons in single occupied orbitals have to have the same spin to maximize the total spin.