Answer: The concentrations of A , B , and C at equilibrium are 0.1583 M, 0.2583 M, and 0.1417 M.
Explanation:
The reaction equation is as follows.

Initial : 0.3 0.4 0
Change: -x -x x
Equilbm: (0.3 - x) (0.4 - x) x
We know that, relation between standard free energy and equilibrium constant is as follows.

Putting the given values into the above formula as follows.


x = 0.1417
Hence, at equilibrium
= 0.1583 M
= 0.2583 M
There is one missing point in the question.
The formula to find an increase in boiling Temperature is :
ΔT = kb x M
ΔT = is the increase in boiling Temperature
Kb = Boiling point constant of the Solvent
M = Molarity
You did not provide the Kb. If you have it, you just have to insert it to the formula to find the ΔT.
And assuming that the other solution is water, you just have to add it up with 100 Celcius
Their valence electrons don't give them the ability to bond, they are also not in need to any electrons, since they won't get an octet soon.