Vapors of methanol are oxidized in a rigid 10.0 L vessel at constant temperature according to the balanced equation
2 CH₃OH(g) + O₂(g) → 2 CH₂O(g) + 2 H₂O(g)
Initially, the vessel contains 0.800 mol of O₂. After 15.0 s, the amount of O₂ has decreased to 0.720 mol.
(a) Calculate the average rate of disappearance of O₂ over the first 15.0 s, expressing your answer in mol⋅L−1s−1.
(b) Determine the average rate of appearance of H₂O during the same interval, in mol⋅L−1s−1.
(c) Convert the rate obtained in part (b) to molecules of H₂O produced per second in the vessel.
(d) Using stoichiometry, calculate the net change in the total number of moles of gas present in the vessel over the 15.0 s interval. Based on this result and the ideal gas law, predict whether the total pressure in the rigid vessel increases, decreases, or remains constant, and justify your reasoning.