Question

2 HI(g)--><--H2(g) + I2(g)

When a sufficiently large sample of HI(g) is introduced into an evacuated vessel at 643 K, the equilibrium concentration of I2(g) is found to be 0.248 M.

Calculate the concentration of HI in the equilibrium mixture. M.

Please help! I have no idea how to do this

Answer 1

This can be solve without an equilibrium constant and none is listed. If one were this is what you do.

..............2HI--> H2 + I2
Kc = (H2)(I2)/(HI)^2
You know (I2) from the problem. (H2) = (I2)
Plug in those values and solve for (HI) at equilibrium.