Math Problem Statement

Reaction: 𝒂𝑨 + 𝒃𝑩 + 𝒄π‘ͺ β†’ 𝒅𝑫 + 𝒆𝑬 Expt 1: Vary [A] while keeping all other conditions the same. Use Excel to determine the reaction with respect to A. (See prelab background and Excel video for assistance in understanding this calculation.) Save your Excel file! Reaction order with respect to 𝐴: ______________

Time (s) [A], M 10 0.166 18 0.144 26 0.122 34 0.0998 42 0.0760 50 0.0523 58 0.0304

Solution

To determine the reaction order with respect to AA using the given data, we need to analyze how the concentration of AA changes over time and compare this with a reaction order model.

Steps to Determine the Reaction Order with Respect to AA:

  1. Logarithmic Data Plotting:

    • First, plot ln⁑[A]\ln[A] vs. time in Excel.
    • If the plot is linear, the reaction is first order with respect to AA.
    • If the plot of 1/[A]1/[A] vs. time is linear, the reaction is second order with respect to AA.
    • If a plot of [A][A] vs. time is linear, the reaction is zero order with respect to AA.
  2. Calculate Necessary Data:

    • Calculate ln⁑[A]\ln[A] and 1/[A]1/[A] for each time point to check for linearity in different plots.
    • Use the given concentrations of AA at different times and the time values to fill in the new columns.
  3. Create the Plots:

    • Plot [A][A] vs. time.
    • Plot ln⁑[A]\ln[A] vs. time.
    • Plot 1/[A]1/[A] vs. time.
  4. Determine the Linear Fit:

    • The graph that produces the best linear fit (i.e., the highest R2R^2 value) will indicate the reaction order with respect to AA.

Example Calculations:

For each time, we can compute:

  • ln⁑[A]\ln[A] (natural logarithm of [A][A]).
  • 1/[A]1/[A] (reciprocal of [A][A]).
Time (s)[A] (M)ln⁑[A]\ln[A]1/[A]1/[A]
100.166-1.7966.024
180.144-1.9376.944
260.122-2.1048.197
340.0998-2.30810.02
420.0760-2.57613.16
500.0523-2.95019.12
580.0304-3.49232.89

What to Do in Excel:

  1. Enter the data for time and [A][A].
  2. Create new columns for ln⁑[A]\ln[A] and 1/[A]1/[A].
  3. Plot:
    • [A][A] vs. time
    • ln⁑[A]\ln[A] vs. time
    • 1/[A]1/[A] vs. time
  4. Check which plot shows the best straight-line fit.
  5. The slope of the linear plot will give you the rate constant kk and the linearity (RΒ² value) will confirm the order of the reaction with respect to AA.

Expected Results:

  • If the ln⁑[A]\ln[A] vs. time plot is linear, the reaction is first order.
  • If the 1/[A]1/[A] vs. time plot is linear, the reaction is second order.
  • If [A][A] vs. time is linear, the reaction is zero order.

Would you like a more detailed explanation on using Excel or analyzing the results?


Related Questions:

  1. How can you calculate the rate constant kk from a first-order reaction graph?
  2. What role does the reaction order play in determining the half-life of a reactant?
  3. How would you use a method of initial rates to determine reaction order with respect to other reactants?
  4. What is the integrated rate law for second-order reactions?
  5. How does temperature affect the reaction rate and reaction order?

Tip: Always compare the RΒ² values from different graphs to determine which reaction order fits best.

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Math Problem Analysis

Mathematical Concepts

Reaction Kinetics
Logarithmic Functions
Rate Laws

Formulas

First-order reaction: ln[A] = -kt + ln[A0]
Second-order reaction: 1/[A] = kt + 1/[A0]
Zero-order reaction: [A] = -kt + [A0]

Theorems

Rate Law Equations for Reaction Orders

Suitable Grade Level

Grades 11-12 (Advanced Chemistry)