The decomposition of gaseous dimethyl ether at ordinary pressures is first-order. Its half-life is 25.0 minutes at 500 C: CH3OCH3(g) CH4(g) + CO(g) + H2(g) (a) Starting with 8.00 g of dimethyl ether, what mass remains (in grams) after 125 minutes and after 145 minutes? (b) Calculate the time in minutes required to decrease 7.60 ng (nanograms) to 2.25 ng. (c) What fraction of the original dimethyl ether remains after 150 minutes?

Nitrogen monoxide reacts with oxygen to give nitrogen dioxide. 2NO(g)+O2(g)2NO2(g) The rate law is [NO]/t = k[NO]2[O2], where the rate constant is 1.16 103 L2/(mol2 s) at 339oC. A vessel contains NO and O2 at 339oC. The initial partial pressures of NO and O2 arc 155 mmHg and 345 mmHg, respectively. What is the rate of decrease of partial pressure of NO (in mmHg per second)? (Hint: From the ideal gas law, obtain an expression for the molar concentration of a particular gas in terms of its partial pressure.)

Ozone, O3, in the Earths upper atmosphere decomposes according to the equation 2 O3(g) 3 O2(g) The mechanism of the reaction is thought to proceed through an initial fast, reversible step followed by a slow, second step. Step 1: Fast, reversible O3(g) O2(g) + O(g) Step 2: Slow O3(g) + O(g) 2 O2(g) (a) Which of the steps is rate-determining? (b) Write the rate equation for the rate-determining step

Nitrosyl bromide, NOBr, is formed from NO and Br2: 2 NO(g) + Br2(g) 2 NOBr(g) Experiments show that this reaction is second-order in NO and first-order in Br2. (a) Write the rate equation for the reaction. (b) How does the initial reaction rate change if the concentration of Br2 is changed from 0.0022 mol/L to 0.0066 mol/L? (c) What is the change in the initial rate if the concentration of NO is changed from 0.0024 mol/L to 0.0012 mol/L?

At 500 K in the presence of a copper surface, ethanol decomposes according to the equation C2H5OH(g)CH3CHO(g)+H2(g) The pressure of C2H5OH was measured as a function of time and the following data were obtained: Time(s) PC2H5OH(torr) 0 250. 100. 237 200. 224 300. 211 400. 198 500. 185 Since the pressure of a gas is directly proportional to the concentration of gas, we can express the rate law for a gaseous reaction in terms of partial pressures. Using the above data, deduce the rate law, the integrated rate law, and the value of the rate constant, all in terms of pressure units in atm and time in seconds. Predict the pressure of C2H5OH after 900. s from the start of the reaction. (Hint: To determine the order of the reaction with respect to C2H5OH, compare how the pressure of C2H5OH decreases with each time listing.)

For the reaction 4NO2(g)+O2(g)2N2O5(g) (a) express the rate of formation of N2O5 in terms of the rate of disappearance of O2. (b) suppose the rate of disappearance of O2 is 0.0037 mol L1 s1. Calculate the rate of disappearance of NO2.