Potential Energy (kJ) Consider these three reactions as the elementary steps in the mechanism for a chemical reaction. (i) Cl₂ (g) + Pt (s) → 2Cl (g) + Pt (s) Ea = 1550 kJ (ii) Cl (g) + CO (g) + Pt (s) → CICO (g) + Pt (s) Ea = 2240 kJ (iii) Cl (g) + CICO (g) → Cl₂CO (g) Ea = 2350 kJ 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 a. Draw the potential energy diagram for the reaction. Label the data points for clarity. The potential energy of the reactants is 600 kJ 0 -200 -400- -600 -800- Reaction Progress AH = -950 kJ AH=575 kJ ΔΗ = - 825 kJ b. What is the overall chemical equation? c. What is the overall change in enthalpy for the above chemical reaction?
Consider these three reactions as the elementary steps in the mechanism for a
(i) Cl2 (g) + Pt (s) à 2Cl (g) + Pt (s) Ea = 1550 kJ ∆H = – 950 kJ
(ii) Cl (g)+ CO (g) + Pt (s) à ClCO (g) + Pt (s) Ea = 2240 kJ ∆H = 575 kJ
(iii) Cl (g) + ClCO (g) à Cl2CO (g) Ea = 2350 kJ ∆H = – 825 kJ
a. Draw the potential energy diagram for the reaction. Label the data points for clarity.
The potential energy of the reactants is 600 kJ.
b. What is the overall chemical equation?
c. What is the overall change in enthalpy for the above chemical reaction?
d. What is the overall amount of activation energy for the above chemical reaction?
e. Which reaction intermediate would be considered a catalyst (if any) and why?
f. If you were to add 2700kJ of activation energy to the reaction, would you be able to make the reaction reverse itself (i.e. have the products become reactants)? Justify your answer.
g. If you were to added a positive catalyst to step (iii) what would the end result be? Justify your
prediction.
h. Your friend is looking at your graph and states that she believes that step (ii) is the rate determining step. Do you agree with her? Justify your reasoning.
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