126. Solving a chemistry problem

The kinetics of chemical reactions A (Table 2) was studied by measuring the total pressure Ptot (Pa) of the gaseous mixture at different times of the reaction t at a constant volume V = 1 m3 and temperature T. All substances involved in the reaction are ideal gases.
Using the data on the total pressure of the reaction mixture versus the reaction time, as well as the data on the dependence of the reaction rate constant on the temperature, answer the following questions.
1. Derive a formula for calculating the partial pressure of the initial substance of the chemical reaction A, using the values ​​of the total pressure of the reaction mixture.
2. Write an equation for calculating the concentration of the starting substance in moles per decimeter (mol/dm3) using the Mendeleev-Clapeyron equation, taking into account the dimensions of the quantities used. Using this equation, calculate the concentrations of the initial substance Cin (mol/dm3) at different times of the reaction t.
3. Determine the reaction order graphically from three possible values ​​of the reaction order: 1, 2 and 3. To do this, plot the dependencies ln(Cin)-f(t), 1/Cin-f(t) and 1/Cin2-f (t)
4. Confirm the correctness of the found value of the reaction order by the substitution method. Determine the reaction rate constant for all values ​​of time (t), find the average value of the reaction rate constant and indicate its dimension.
5. On the graph corresponding to the found order of the reaction, determine the graphical value of the reaction rate constant, compare it with the average value.
6. Determine the order of the reaction according to the graphical modification of the van´t Hoff method (differential method). To do this, it is necessary to plot the dependence Cin-f(t). Determine graphically at three times the reaction rate (as the tangent of the slope of the tangent). Graphically define three concentrations,
corresponding to the selected time values, and then, using the ln(W)-f(lnCx) dependency graph, determine the reaction order as the tangent of the slope of the straight line with the positive direction of the abscissa axis.
7. Write the kinetic equation for the rate of reaction A in differential form. Determine if the reaction order and molecularity match in your case.
8. Using the value of the rate constant, determine the amount of the initial substance in 1 dm3 that has reacted by the time t1 (the amount of the reacted substance Cx or x). Using the equation obtained in paragraph 2, find the amount of the reacted substance. Then, using the equation from paragraph 1, find the total pressure in the system at time t1 in pascals.
9. Determine the half-life for reaction A in seconds.
10. Using the average value of the reaction rate constant A from step 4 at temperature T, as well as the rate constants k1 and k2 at temperatures T1 and T2 (Table 2), plot the Ink-f(1/T) dependence. Determine the activation energy value graphically in
joules per mole (J/mol) and kilojoules per mole (kJ/mol).
11. Calculate analytically the activation energy in the units indicated above and compare with the graphically found value.
12. Determine the pre-exponential factor in the Arrhenius equation for reaction A
13. Determine the reaction rate constant at temperature (see Table 2).
14. Determine the temperature coefficient of the reaction rate γ in the temperature range T1 and T2. How many times will the reaction rate change if the temperature T1 is increased by 25°?
OPTION 7


2H2C=HC–CH=CH2 →CH2=C <(CH2)4 (CH2)2

T = 599 K
t1 = 900 s
Reaction time 0 860 2200 4080 5400

Reaction mixture pressure 84.2 76.8 69.5 63.3 60.4
Reaction temperature T1 = 573 T2 = 622 T3 = 605
Rate constant k1 = 9.85 k2 = 44.5