4 and 2 electrons are present.
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
Considering the definition of molarity, the molar concentration is 0.294
.
Molarity reflects the concentration of a solution indicating the number of moles of solute that are dissolved in a given volume.
The molarity of a solution is calculated by dividing the moles of the solute by the volume of the solution:

Molarity is expressed in units
.
In this case, you know:
- amount of moles of solute= 0.250 moles
- volume= 0.850 L
Replacing in the definition of molarity:

Solving:
molarity= 0.294 
Finally, the molar concentration is 0.294
.
Learn more about molarity with this example: brainly.com/question/15406534?referrer=searchResults
Answer:
They are composed of hydrogen and helium