kinetics_13

# Its original 2 a value t value 0 kt1 2 0 12

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Unformatted text preview: the half-life of a first order reaction is known, the When rate constant can easily be calculated with the above equation or vice verse. Half Life of First Order Half Integrated Rate Law Integrated Second Order Reactions: A → Products Rate = k[A]2 Rate A + B → Products Rate = k[A][B] For one substance ∆[ A ] Rate = ∆t 1 1 = kt [A]t [A]0 Integrated Rate Laws Integrated Second Order Reactions 1 1 = kt [A]t [A]0 Half-life for 2nd Order 1 t1 = k [ A] 0 2 Half-life for Second Order Reactions Half-life Zero Order Reactions Zero They do not depend on the They concentration of any reactant. concentration A products t t 0 0 ∫ ∆[ A] = -∫ k∆t Rate = k ∆[ A ] Rate = ∆t ∆[ A ] k=∆t [A]t - [A]0 = -kt Zero Order Reactions Zero Integrated Rate Law [A]t - [A]0 = -kt Half-life expression [A]0 t1/2 = 2k Integrated Rate Laws Integrated Zero Order reactions [A]t - [A]0 = kt First Order reactions [A ] ln [ A] t = -kt 0 Second Order reactions 1 1 = kt [A]t [A]0 Integrated Rate Laws The hydrolysis of sucrose in water to glucose and fructose The is a first order reaction at 25 C. It takes 3.33 hours for the [sucrose] to drop from 1.20 M to 0.60 M. How many hours are required for the [ ] to change from 0.800 M to 0.0500 M? might need half-life equation M? A) 0.90 hr b) 1.33 hr c) 13 3 hr d) 5.63 hr Integrated Rate Laws Integrated Iodine atoms combine to form molecular iodine in the gas phase. I(g) + I(g) → I2(g) This reaction follows second-order kinetics with k = 7.0 x 10–1 M–1s–1 at 23°C. (a) If the initial concentration of I was 0.086 M, 10–1 calculate the concentration after 2.0 min. A) 3.83x10-36 M b) 2.85 M (b) Calculate the half-life of the reaction if the initial concentration of I (b) is 0.60 M and if it is 0.42 M. is c) 0.010 M d) 0.076 M Determination of Rate Law by the Graph Method by Rate Data For 2 NO2 → 2 NO + O2 Time (hrs.) 0 30 60 Partial Pressure NO2, Pressure mmHg mmHg 100.0 62.5 45.5 ln(PNO2) 1/(PNO2) 4.605 4.135 3.817 0.01000 0.01600 0.02200 90 120 150 180 35.7 29.4 25.0 21.7 3.576 3.381 3.219 3.079 0.02800 0.03400 0.04000 0.04600 210 240 19.2 17.2 2.957 2.847 0.05200 0.05800 37 37 Rate Data Graphs For Rate 2 NO2 → 2 NO + O2 Partial Pressure NO2, mmHg vs. Time 100.0 90.0 Pressure, (mmHg) 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 0 50 100 150 Time, (hr) 200 250 Rate Data Graphs For Rate 2 NO2 → 2 NO + O2 ln(P NO2) vs. Time 4.8 4.6 4.4 4.2 ln(pressure) 4 3.8 3.6 3.4 3.2 3 2.8 2.6 2.4 0 50 100 150 Time (hr) 200 250 Rate Data Graphs For Rate 2 NO2 → 2 NO + O2 1/(P NO2) vs Time 0.07000 0.06000 Inverse Pressure, (mmHg -1 ) 1/PNO2 = 0.0002(time) + 0.01 0.05000 0.04000 0.03000 0.02000 0.01000 0.00000 0 50 100 150 Time, (hr) 200 250 Reaction Mechanism Reaction Is a sequence of molecular events, or steps, that Is defines the path by which reactants become products. products. The single steps in a mechanism are called The elementary steps (reactions). elementary The sum of the elementary steps results in the The overall reactio...
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