For N2 + O2 forming 2NO, Kc = 4.1 x 10^-4 with [N2] = 0.036 M and [O2] = 0.0089 M. What is [NO]?

1. The expression is Kc = [NO] squared divided by ([N2] x [O2]). 2. Rearrange to make the unknown the subject: [NO] squared = Kc x [N2] x [O2]. 3. Multiply the two known concentrations: 0.036 x 0.0089 = 3.204 x 10^-4. 4. Multiply by the constant: 4.1 x 10^-4 x 3.204 x 10^-4 = 1.31 x 10^-7. 5. That figure is the square of the answer, not the answer itself. 6. Take the square root: the root of 1.31 x 10^-7 is 3.6 x 10^-4. 7. So the nitrogen monoxide concentration is 3.6 x 10^-4 mol per litre. 8. Stopping at 1.3 x 10^-7 is the trap of forgetting the square root at the last step. _Source: OpenStax Chemistry (CC BY 4.0), Ch 13 "Fundamental Equilibrium Concepts", section 13.4 Equilibrium Calculations_