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Ch.14 - Chemical Kinetics
All textbooksTro 4th EditionCh.14 - Chemical KineticsProblem 88
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Chapter 14, Problem 88

At 400 K, oxalic acid decomposes according to the reaction: H2C2O4(g) → CO2(g) + HCOOH(g). In three separate experiments, the initial pressure of oxalic acid and the final total pressure after 20,000 seconds are measured. Experiment: 1) PH2C2O4 at t = 0: 65.8, PTotal at t = 20,000 s: 94.6; 2) PH2C2O4 at t = 0: 92.1, PTotal at t = 20,000 s: 132; 3) PH2C2O4 at t = 0: 111, PTotal at t = 20,000 s: 160. Find the rate law of the reaction and its rate constant.

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Identify the reaction: \( \text{H}_2\text{C}_2\text{O}_4(g) \rightarrow \text{CO}_2(g) + \text{HCOOH}(g) \). Note that the decomposition of one mole of \( \text{H}_2\text{C}_2\text{O}_4 \) produces one mole of \( \text{CO}_2 \) and one mole of \( \text{HCOOH} \).
Calculate the change in pressure (\( \Delta P \)) for each experiment by subtracting the initial pressure of \( \text{H}_2\text{C}_2\text{O}_4 \) from the total pressure at \( t = 20,000 \) seconds.
Determine the concentration of \( \text{H}_2\text{C}_2\text{O}_4 \) that has decomposed in each experiment using the relation: \( \Delta P = P_{\text{CO}_2} + P_{\text{HCOOH}} = 2x \), where \( x \) is the change in pressure due to the decomposition of \( \text{H}_2\text{C}_2\text{O}_4 \).
Use the initial pressures and the changes in pressure to determine the order of the reaction by comparing the ratios of the rates of reaction (\( \Delta P / \Delta t \)) to the initial pressures raised to the power of the reaction order (\( n \)).
Once the order is determined, use the rate law \( \text{Rate} = k [\text{H}_2\text{C}_2\text{O}_4]^n \) to calculate the rate constant \( k \) for each experiment and find an average value.
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Open Question
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Textbook Question

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