A quantity of HI was sealed in a tube, heated to 425°C, and held at this temperature until equilibrium was reached. The concentration of HI in the tube at equilibrium was found to be 0.0706 moles/liter. Calculate the equilibrium concentration of H2 (and I2). (Hint: H2 and I2 are equal).
For the reaction: H2(g) + I2(g) ßà 2 HI(g) Kc = 54.6 at 425°C.
a. 4.78 × 10-3M
b. 9.55 × 10-3M
c. 2.34 × 10-3M
d. 1.17 × 10-3M
e. 1.85 × 10-4M
H2(g) + I2(g) ------>2 HI(g)
Kc for the reaction
Kc = [HI]2 / [H2] [I2]
but he has given hint (Hint: H2 and I2 are equal)
so [H2] = [I2]
now the above expression will be
Kc = [HI]2 / [H2] [H2]
he has given Kc = 54.6 and
concentration of [HI] at equilibrium is 0.0706 moles/liter
put these values in above equation
54.6 = [0.0706]2 / [H2] [H2]
[H2]2 = 0.00498 / 54.6
[H2]2 = 9.128 x 10-5
[H2] = squareroot of 9.128 x 10-5
[H2] = 0.00955
[H2] = 9.55 × 10-3M
but at equilibrium concentration of [H2] = [I2]
so concentration of [I2] = 9.55 × 10-3M
answer is b. 9.55 × 10-3M
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