475

15 2. Classification of reactions used in kinetics. 3. Dependence of the reaction rate on concentration. The basic law of kinet- ics. The order and molecular nature of the chemical reaction. 4. First-order kinetics equations. The half-transformation period. 5. Dependence of the reaction rate on temperature. The empirical rule of Van’t Hoff. Activation energy; Arrhenius equation. 7. Catalysis. Enzymatic catalysis. The Michaelis-Menten equation and its analysis. Input test-control on the topic «Chemical kinetics». Homework exercises. 1. The rate of some simple reaction is 0.01 mol/ls. Determine the concentra- tion of the starting substance after 1 minute from the start of the reaction if the initial concentration of the reagent was 2 mol/l. Answer : 1.4 mol/l 2. Write the expression for the «effective mass» law for the reactions given. Determine the reaction order and reaction molecularity: a) N 2 O 5 (g) → N 2 O 3 (g) + O 2 (g) b) 2H 2 S (g) + SO 2 (g)→ 3S (s) + 2H 2 O (g) c) I 2 (g) + H 2 (g) → 2HJ (g) d) Mg (HCO 3 ) 2 (s) → H 2 O (g) + CO 2 (g) + MgCO 3 (s) 3.How changes of the rate of synthesis of sulfur oxide (VI) from sulfur oxide (IV) when the concentration of starting materials is decreased by a factor of two? Answer : it will decrease 8 times. 4. How is changed the rate of chemical reaction when the reaction mixture is cooled by 30°C, if the temperature coefficient is 3? Answer : it decreases 27 times. 5. The half-life of radioactive carbon is 20.5 minutes. Calculate the rate constant. Answer : 0.0338 min –1. 6. Under storing aspirin tablets, it is established that the decomposition constant at 20 °C is 5×10 –8 min –1. Determine the shelf life of aspirin at 20 °C (decomposition time 10% of the substance). Answer : 4 years. 7. What is the activation energy, if the rate of increase in temperature from 290 to 300 K doubled? Answer : 49.9 kJ/mol. 8. The activation energy of the decomposition reaction of hydrogen iodide 2HI ⇄ H 2 + I 2  in a gas mixture at 800 K is 190 kJ/mol. It decreases to 60 kJ/molin the presence of platinum. Determine how many times the reaction rate in the presence of platinum is higher. Answer : 3,2×10  8.