Answer:
3.5 mol·L⁻¹
Explanation:
1. Set up an ICE table.
[tex]\begin{array}{cccccc}\text{2NO} & + & \text{I}_{2} &\, \rightleftharpoons \, & \text{2NOI} & & \\ 2.0 & & 4.0 & & 1.0 & & \\ -2x & & -x & & +2x & & \\ 2.0-2x & & 4.0-x & & 1.0+2x & & \\\end{array}[/tex]
2. Solve for x
The equilibrium concentration of NO is 1.0 mol·L⁻¹, so
1.0 = 2.0 - 2x
2x + 1.0 = 2.0
2x = 1.0
x = 0.5
3. Calculate the equilibrium concentration of I₂
[I₂] = 4.0 - x = 4.0 - 0.5 = 3.5 mol·L⁻¹
