How to use the pseudo first order rate constant calculator
Find the effective first-order rate constant when one reactant is in large excess. Enter second-order rate constant, excess reactant concentration in the fields above; the pseudo first order constant, half-life are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “pseudo first order”, “excess reagent rate constant”, “k prime equals k2 times B”, “calculate pseudo first order rate constant”, “find pseudo first order constant”.
Formula
Variables
- k2 — Second-order rate constant (M⁻¹s⁻¹)
- B0 — Excess reactant concentration (M)
Worked example
With second-order rate constant = 0.05 M⁻¹s⁻¹, excess reactant concentration = 0.5 M, the calculator gives pseudo first order constant ≈ 0.025 s⁻¹; half-life ≈ 27.72589 s.
Frequently asked questions
What is the pseudo first order rate constant calculator used for?
Find the effective first-order rate constant when one reactant is in large excess. It helps with questions such as “pseudo first order”, “excess reagent rate constant”, “k prime equals k2 times B”.
What is the formula for the pseudo first order rate constant calculation?
Pseudo first order constant (s⁻¹) = k2 × B0. Half-life (s) = ln(2) / [Pseudo first order constant]. Here k2 is second-order rate constant (M⁻¹s⁻¹), B0 is excess reactant concentration (M).
What inputs do I need for the pseudo first order rate constant calculator?
You need second-order rate constant in M⁻¹s⁻¹, excess reactant concentration in M. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the pseudo first order rate constant calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the pseudo first order rate constant result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.