Answer:
0.146 M
Explanation:
Equation for the reaction :
2A(aq) ↔ B(aq) + C(aq)
= 65
Molar concentration of A = 
= 2.5 M
2A(aq) ↔ B(aq) + C(aq)
Initial 2.50 0 0
Change - 2x + x + x
Equilibrium 2.50 - 2x +x +x
![K_c =\frac {[B][C]}{[A]^2}](https://tex.z-dn.net/?f=K_c%20%3D%5Cfrac%20%7B%5BB%5D%5BC%5D%7D%7B%5BA%5D%5E2%7D)
![65 = \frac{[x][x]}{[2.5-2x]^2}](https://tex.z-dn.net/?f=65%20%3D%20%5Cfrac%7B%5Bx%5D%5Bx%5D%7D%7B%5B2.5-2x%5D%5E2%7D)
![65 = \frac{[x]^2}{[2.5-2x]^2}](https://tex.z-dn.net/?f=65%20%3D%20%5Cfrac%7B%5Bx%5D%5E2%7D%7B%5B2.5-2x%5D%5E2%7D)
![65 = (\frac{[x]}{[2.5-2x]})^2](https://tex.z-dn.net/?f=65%20%3D%20%28%5Cfrac%7B%5Bx%5D%7D%7B%5B2.5-2x%5D%7D%29%5E2)
![\sqrt 65 = \sqrt {(\frac{[x]}{[2.5-2x]})^2}](https://tex.z-dn.net/?f=%5Csqrt%2065%20%3D%20%20%5Csqrt%20%7B%28%5Cfrac%7B%5Bx%5D%7D%7B%5B2.5-2x%5D%7D%29%5E2%7D)

8.062(2.5 - 2x) = x
20.155 - 16.124x = x
20.155 = 16.124x+x
20.155 = 17.124x
x = 
x = 1.177
[A] = 2.5 - 2x
= 2.5 - 2(1.177)
= 0.146 M
Therefore, the equilibrium concentration of A = 0.146 M
Hydrogen only has 1 electron so not A.
Barium has 2 valence electrons so answers B!
Answer: A thermal energy
Explanation: come on that one was easy.