
Answer:
Increases rate of rxn 9X
Explanation:
Given 4NO + Oâ‚‚ + 2Hâ‚‚O => 4HNOâ‚‚
Rate = k[NO]²[O₂] ; if [O₂] is kept constant => Rate = k[NO]²
For 2nd order reactions Rate = k[A]². If [A] = a, 2a, 3a … then the Rate trend for a 2nd order reaction is …
Rate 1 = k(a)² = ka²
Rate 2 = k(2a)² = 4ka²
Rate 3 = k(3a)² = 9ka²  <= 3X increase in concentration
Rate 4 = k(4a)² = 16ka²
Increasing the concentration of NO by 3 times while keeping concentrations of Oâ‚‚ and Hâ‚‚O constant  increases rate of reaction by 9 times. Â