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increase, lower C) decrease, lower D) increase, higher E) decrease, constant 67)

ID: 694149 • Letter: I

Question

increase, lower C) decrease, lower D) increase, higher E) decrease, constant 67) During the combustion of ethylene gas, C2Hs, carbon dioxide is produced and the rate of disappearance of O2 is 0.13 M s1. What is the rate of appearance (M s-) of CO2? A) 0.043 B) 0.39 C) 0.087 D) 0.20 E) 0.26 68) The rate constant for a particular second-order reaction is 0.47 M s1. If the initial concen s for the concentration to decrease to 0.20 mol/L reactant is 0.25 mol/L, it takes A) 2.1 B) 1.4 c) 1.0 D) 0.47 E) 0.20 69) For the reaction CH, (g) C2H4 (g) + H2 (g) 1° is +137 kJ/mol and ASo is +120 J/K . mol. This reaction is ntoneous at all temperatures

Explanation / Answer

67) C2H4(g) + 3O2(g) ---> 2co2(g) + 2H2O(g)

rate = -1/3d[O2]/dt = +1/2d[CO2]/dt

rate of appearance of co2 = d[CO2]/dt = 2/3*d[O2]/dt

                          = 2/3*0.13

                          = 0.0867

answer: c) 0.087

68) second order kinetics

k = x/t*a*(a-x)

a = initial concentration = 0.25 M

a-x = 0.2 M

x = 0.25-0.2 = 0.05 M

t = ?

0.47 = 0.05/(t*0.25*0.2)

t = 2.13 sec

answer: A.2.1