Rate Law Calculator

The Rate Law Calculator determines the rate constant (k) for a chemical reaction — the proportionality factor that describes how fast reactants convert to products under given conditions. Choose From Rate Experiment and enter your reaction rate, concentrations [A] and [B], and their reaction orders (m, n), or switch to From Integrated Rate Law and enter your initial concentration [A]₀, final concentration [A]ₜ, and time (t) to get the rate constant, full rate law expression, half-life, and overall reaction order.

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Results

Rate Constant (k)

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Rate Law Expression

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Half-Life

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Overall Reaction Order

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Frequently Asked Questions

How do I calculate the rate constant from experimental data?

For experimental data, use the rate law equation: rate = k[A]^m[B]^n. Rearrange to solve for k: k = rate / ([A]^m × [B]^n). Enter your measured rate and concentrations along with the reaction orders to calculate k.

What is the difference between zero, first, and second-order reactions?

Zero-order: Rate is independent of concentration. First-order: Rate is proportional to concentration. Second-order: Rate is proportional to concentration squared. Each has different integrated rate laws and half-life expressions.

How do I determine the order of reaction?

The reaction order is determined experimentally by measuring how the rate changes with concentration. Plot concentration vs time data and analyze the linearity of different transforms (ln[A] vs t for first-order, 1/[A] vs t for second-order).

What factors affect the rate constant?

The rate constant depends primarily on temperature (Arrhenius equation), the presence of catalysts, and the activation energy of the reaction. It's independent of concentration but increases exponentially with temperature.

How is half-life related to the rate constant?

For first-order reactions: t₁/₂ = ln(2)/k. For second-order: t₁/₂ = 1/(k[A]₀). For zero-order: t₁/₂ = [A]₀/(2k). The relationship varies with reaction order.

Can I use this calculator for complex multi-step reactions?

This calculator is designed for elementary reactions or reactions that follow simple rate laws. For complex mechanisms, you'll need to determine the rate-determining step and its corresponding rate law first.