Explanation:
The reaction equation will be as follows.

Hence, moles of Na = moles of electron used
Therefore, calculate the number of moles of sodium as follows.
No. of moles = 
=
(as 1 kg = 1000 g)
= 195.65 mol
As, Q =
where F = Faraday's constant
= 
=
mol C
Relation between electrical energy and Q is as follows.
E = 
Hence, putting the given values into the above formula and then calculate the value of electricity as follows.
E = 
= 
= 
As 1 J =
kWh
Hence,
kWh
= 3.39 kWh
Thus, we can conclude that 3.39 kilowatt-hours of electricity is required in the given situation.
Answer:- 544.5 mL of water need to be added.
Solution:- It is a dilution problem. The equation used for solving this type of problems is:

where,
is initial molarity and
is the molarity after dilution. Similarly,
is the volume before dilution and
is the volume after dilution.
Let's plug in the values in the equation:



Volume of water added = 907.5mL - 363mL = 544.5 mL
So, 544.5 mL of water are need to be added to the original solution for dilution.