Help with question 11.43 6th edition [ENDORSED]

[Ashley Kenney 1E]

When determining the equilibrium relation, I understand where the terms x^2 and 2x come from, but I don't quite understand why we subtract 2x from the initial partial pressure of NO to create the expression of 1-2x. Can someone please explain this? Thank you!

[Tam To 1B]

On the ICE table, you have to find initial molar concentration, change in molar concentration, and the equilibrium molar concentration. Since you are initially given 1.0 mol/L NO, the change would be -2x since you have the coefficient 2NO in the reaction. In order to calculate equilibrium, you subtract the change from the initial which then gives you 1.0-2x as the equilibrium molar concentration of NO.

[Ashley Kenney 1E]

Oh that makes sense. Thank you!