Formula Used:
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Definition: The average life-time for a set of parallel reactions is the characteristic time period during which the concentration of reactants decreases to half its initial value through multiple simultaneous reaction pathways.
Purpose: This calculation is essential in chemical kinetics to understand the overall behavior of systems where multiple reaction pathways compete.
The calculator uses the formula:
Where:
Explanation: The natural logarithm of 2 (0.693) is divided by the sum of all parallel reaction rate constants to determine the average lifetime.
Details: Understanding the average life-time helps chemists predict reaction durations, design industrial processes, and analyze complex reaction mechanisms.
Tips: Enter the rate constants for all three parallel reactions in reciprocal seconds (s⁻¹). At least one rate constant must be greater than zero.
Q1: What does the 0.693 represent in the formula?
A: This is the natural logarithm of 2 (ln(2)), which appears in all half-life calculations for first-order kinetics.
Q2: Can I use this for more than three parallel reactions?
A: Yes, simply extend the formula by adding additional rate constants to the denominator.
Q3: What if one rate constant is much larger than the others?
A: The fastest reaction will dominate, and the average lifetime will approach the lifetime of that single reaction.
Q4: How do I obtain the individual rate constants?
A: They are typically determined experimentally through kinetic studies of each isolated reaction pathway.
Q5: Does this apply to non-first-order reactions?
A: No, this specific formula only applies to parallel first-order reactions or elementary steps.