Mass percentage of sodium chloride(NaCl) in ocean waters = 3.5 %
That means 3.5 g sodium chloride(NaCl) is present for every 100 g of ocean water.
The given mass of sodium chloride(NaCl) is 45.8 g
Calculating the mass of ocean waters that would contain 45.8 g sodium chloride(NaCl):

= 1309 g ocean water
Therefore, 45.8 g sodium chloride is present in 1309 g ocean water.
The reaction CFCl3 + UV Light -> CFCl2 + Cl does not need another reactant as with CFCl3 because the reaction itself is reactive to light. Note that there are reactions that are sensitive to light to form products and when this type of reaction are not exposed to light, no reaction occurs.
Answer:
1,070.41 grams of DDT will be formed .Explanation:
1) 
Moles of chlorobenzene = 
According to reaction, 2 moles of chloro benzene reacts with 1 mole of chloral . Then 10.64 moles of chloro benzene will react with :
of chloral
2) Moles of chloral = 
According to reaction, 1 moles of chloral reacts with 2 mole of chlorobenzene . Then 3.0915 moles of chloral will react with :
of chloro benzene
As we can see that chloral is in limiting amount and chloro benzene is in excessive amount. So, amount of DDT will depend upon amount of chloral.
According to reaction, 1 mole chloral gives 1 mole DDT.Then 3.0195 moles of chloral will give :

Mass of 3.0195 moles of DTT :
3.0195 mol × 354.5 g/mol = 1,070.41 g
1,070.41 grams of DDT will be formed .