Review Problems

Water can be made from hydrogen and oxygen: H 2 (g) + O 2 (g) → H 2 O (g) Some experiments are run in a sealed 1 L flask at 350 K to determine the initial rate of reaction for different concentrations of reactants: [H2 ] M[O2] M Rate of formation of H2O M/sec If I began with moles of both reactants, how long would it take to make 0.01 moles of water?

Orders of reaction [H2 ] M[O2] M Rate of formation of H2O M/sec Rate = k[H2] x [O2] y Rate 1 = k[0.050] x [0.100] y Rate 2 = k[0.050] x [0.050] y = [0.100] y = [0.050] y 1.92 =2 y Y =1

Orders of reaction [H2 ] M[O2] M Rate of formation of H2O M/sec Rate = k[H2] x [O2] y Rate 2 = k[0.050] x [0.050] Rate 3 = k[0.100] x [0.025] = [0.100] x = [0.050] x 2.08 =2*2 x 1.04 =2 x X=0

Rate = k[O 2 ] [H2 ] M[O2] M Rate of H2O M/sec M/s = k [0.100 M] K =0.048 s = k [0.050] K =0.05 s =k[0.025] K =0.048 s -1 K avg = s -1

1 st order kinetics ln [O 2 ] t = - kt [O 2 ] 0 2H 2 (g) + O 2 (g) → 2H 2 O (g) If I began with moles of both reactants, how long would it take to make 0.01 moles of water? mol H 2 O * 1 mol O 2 = mol O 2 2 mol H 2 O mol O2 started – mol O2 reacted = mol left

1 st order kinetics ln [O 2 ] t = - kt [O 2 ] 0 Ln (0.045/0.05) = s -1 t t = 2.16 seconds!