Question

The equilibrium constant, Kc, for the following reaction is 1.54E-2 at 643 K.

2HI(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 0.351 M.

Calculate the concentration of HI in the equilibrium mixture. ___M

Answer 1

You really need to find the arrow key and use it.
.....2HI ==> H2 + I2
I....................
C....................
E......y......x....0.351
So if I2 is 0.351 that means H2 is 0.351 (and that does NOT means HI is 0.351).

Write the Kc expression, substitute for H2 and I2 and solve for HI.