How Do You Solve an Equilibrium Problem with Initial Reactants and No Products?

[Bad-Wolf]

1. I am having trouble figuring out how to work the most basic equilibrium problem when there is an initial concentration of reactants only and no product. How am I supposed to find the constant with a zero in my quotient? Here is an example problem:
At 527˚C, K = 0.0160 for the following reaction: 2HI(g) ↔ H2 (g) + I2 (g)
What is the equilibrium concentration of H2
if the initial concentrations of both H2 and I2
= 0.0160 M and the initial concentration of
HI = 0 M?

2. k = product/reactant

3. If I knew where to start I wouldn't need help

 

[Barfolumu]

What will happen to your system if you know that the rxn must be at equilibrium, but it is not currently at equilibrium?

 

[GCT]

1. I am having trouble figuring out how to work the most basic equilibrium problem when there is an initial concentration of reactants only and no product. How am I supposed to find the constant with a zero in my quotient? Here is an example problem:
At 527˚C, K = 0.0160 for the following reaction: 2HI(g) ↔ H2 (g) + I2 (g)
What is the equilibrium concentration of H2
if the initial concentrations of both H2 and I2
= 0.0160 M and the initial concentration of
HI = 0 M?

2. k = product/reactant

3. If I knew where to start I wouldn't need help

You mentioned that K=[product]/[reactants] - write this equation out in full detail and remember that they refer to the equilibrium values.

 

[Kushal]

one way of solving this problem is by breaking it into parts.

initially,

= [I2] = 0.0160 mol/dm3
[HI] = 0 mol/dm3

at equilibrium, let [HI] be x mol/dm3
then, accordingly,

= [I2] = {0.0160 - (x/2)} mol/dm3, because 2 mol HI are produced by using 1 mol H2 and 1 mol I2.

find the equilibrium constant in term of x.
and then solve for x by equation the above expression to 0.0160