One step in the atmospheric formation of nitric acid is believed to proceed through the following elementary reaction.
OH(g) + NO₂(g) + M → HNO₃(g) + M (M is any inert third body such as N₂ or O₂.)
(a) Write the rate law expression for this elementary reaction.
(b) Determine the overall reaction order.
(c) Derive the units of the rate constant k when concentration is expressed in mol L⁻¹ and time in s.
(d) Using kinetic theory and ideal-gas reasoning, explain qualitatively how raising the total pressure (while keeping temperature constant) will affect the numerical value of the rate if the partial pressures of OH and NO₂ remain unchanged.