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Chemistry & Materials Science

Rate of Reaction Calculator

Calculate the exact average rate of a chemical reaction using initial and final concentrations over a specific time interval.

M
M
s
s
Overall Reaction Rate
8.3333e-3 M/s
Species Rate of Change (ΔC/Δt)-8.3333e-3 M/s
Time Elapsed (Δt)60 s
Concentration Change (ΔC)-0.5000 M

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The Speed of Chemistry

In chemistry, kinetics is the study of how fast a reaction occurs. The Rate of Reaction measures the speed at which reactants are consumed to form products.

Just like driving a car where speed is measured in miles per hour (distance over time), the rate of a chemical reaction is measured in Molarity per second (M/sM/s)—the change in concentration over time.

Why Do We Calculate Reaction Rates?

Understanding reaction rates is crucial in both industry and biology. For example, if a pharmaceutical company is synthesizing a new drug, they need to know exactly how long the reaction will take to optimize their factory output. In biology, enzymes act as biological catalysts specifically to speed up reaction rates that would otherwise be too slow to sustain life.

The Mathematical Formula

Rate=−1aΔ[A]Δt=1bΔ[B]Δt\begin{aligned} \text{Rate} = -\frac{1}{a}\frac{\Delta[A]}{\Delta t} = \frac{1}{b}\frac{\Delta[B]}{\Delta t} \end{aligned}

Where:
a, b=
Stoichiometric Coefficients
Δ[A]\Delta[A]=
Change in Reactant Concentration
Δ[B]\Delta[B]=
Change in Product Concentration
Δt\Delta t=
Elapsed Time

Because reactant concentrations decrease over time, their change in concentration (ΔC\Delta C) is technically negative. We multiply the reactant formula by −1-1 so that the overall reaction rate is always expressed as a positive number.

Frequently Asked Questions

Because different molecules are consumed at different speeds. If a reaction uses 2 moles of Hydrogen for every 1 mole of Oxygen, the Hydrogen disappears twice as fast. Dividing by the coefficient normalizes the rate so that the 'Overall Reaction Rate' is a single, consistent number regardless of which molecule you measure.

Usually, no. As the reactants are consumed, there are fewer molecules left to collide with each other. This means the reaction rate typically slows down over time. This calculator measures the 'Average Rate' over the specific time interval you provide.

You can increase the temperature (which gives molecules more kinetic energy), increase the concentration of the reactants (which causes more frequent collisions), or add a catalyst (which lowers the activation energy required).

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