equilibrium constant = 2.180 x 10^6 @ 730 C.

H2 (g) + Br (g) <=> 2HBr (g) (reversible)

startin with 3.20 moles of HBr in a 21.3-L reaction vessel, calculate the concentrations of H2, Br2, and HBr at equilibrium

idk how to start my ice table

(HBr) = 3.20mols/21.3L = about 0.150 but that's an estimate.

It's just like it sounds. I = initial; C = change; E = equilibrium.
I assume you made a typo and meant Br2.
..........H2 + Br2 ==> 2HBr
I.........0.....0......0.150
C.........x.....x.......-x
E.........x.....x......0.150-x

Substitute E line into Kc expression and solve for x and 0.150-x.

shouldn't it be -2x?

To start the ICE table, you need to understand the concept of the ICE table itself. ICE stands for initial, change, and equilibrium. The table is used to keep track of the initial concentrations of reactants and products, the changes in their concentrations during the reaction, and the final equilibrium concentrations.

Let's proceed step by step:

Step 1: Write the balanced chemical equation:
H2 (g) + Br2 (g) ⇌ 2HBr (g)

Step 2: Identify the initial concentrations:
Given that we have 3.20 moles of HBr in a 21.3-L reaction vessel, the initial concentration of HBr is:

[HBr]initial = (moles of HBr) / (volume of reaction vessel)
[HBr]initial = 3.20 moles / 21.3 L

Since there is no mention of the initial concentrations of H2 and Br2, we assume they are zero.

[H2]initial = 0 M
[Br2]initial = 0 M

Step 3: Set up the ICE table with the initial concentrations:
| | H2 | Br2 | 2HBr |
|Initial | 0 | 0 | 3.20 |
|Change | -x | -x | +2x |
|Equilibrium | 0-x | 0-x | 3.20+2x |

Here, x represents the change in concentration, while 2x represents the change for the HBr concentration since the stoichiometry in the balanced chemical equation is 1:1:2.

Step 4: Calculate the equilibrium concentrations:
The equilibrium constant expression for the given reaction is:

Kc = [HBr]^2 / ([H2] * [Br2])

We are given that Kc = 2.180 x 10^6. Plugging in the equilibrium concentrations obtained from the ICE table into this expression, we get:

2.180 x 10^6 = (3.20+2x)^2 / (x * x)

Solving this equation for x will give us the change in concentration at equilibrium. Once we know x, we can substitute it back into the ICE table to find the equilibrium concentrations of H2, Br2, and HBr.