Reaction Rate Calculator
Understanding Reaction Rate
The rate of a chemical reaction describes how quickly reactants are consumed or products are formed over a specific period. It's a fundamental concept in chemical kinetics, allowing us to understand and control chemical processes.
The average rate of a reaction can be calculated using the change in concentration of a reactant or product divided by the change in time. For a reaction where reactant 'A' is consumed to form products, the rate is typically expressed as:
Rate = – (Δ[A] / Δt)
Where:
- Δ[A] is the change in concentration of reactant 'A' (Final Concentration – Initial Concentration). The negative sign is used because the concentration of a reactant decreases over time.
- Δt is the change in time (the time interval over which the concentration change is measured).
The units of reaction rate are typically given in molarity per unit time (e.g., mol/L·s, mol/L·min). A higher rate indicates a faster reaction. This calculator helps you determine this average rate based on measured concentrations at two different time points.
Example:
Consider a reaction where the concentration of a reactant decreases from 1.0 mol/L to 0.5 mol/L over a period of 60 seconds.
- Initial Concentration = 1.0 mol/L
- Final Concentration = 0.5 mol/L
- Time Interval = 60 seconds
Calculation:
Δ[A] = 0.5 mol/L – 1.0 mol/L = -0.5 mol/L
Rate = – (-0.5 mol/L / 60 s) = 0.5 mol/L / 60 s ≈ 0.00833 mol/L·s
This means the reaction is proceeding at an average rate of approximately 0.00833 moles per liter per second.
function calculateReactionRate() {
var initialConcentration = parseFloat(document.getElementById("initialConcentration").value);
var finalConcentration = parseFloat(document.getElementById("finalConcentration").value);
var timeInterval = parseFloat(document.getElementById("timeInterval").value);
var resultDiv = document.getElementById("result");
if (isNaN(initialConcentration) || isNaN(finalConcentration) || isNaN(timeInterval)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (timeInterval <= 0) {
resultDiv.innerHTML = "Time interval must be greater than zero.";
return;
}
var concentrationChange = finalConcentration – initialConcentration;
var reactionRate = – (concentrationChange / timeInterval);
if (reactionRate < 0) {
resultDiv.innerHTML = "The calculated average reaction rate is:
" + reactionRate.toFixed(5) + " mol/L·s (This rate assumes consumption of a reactant. If a product's concentration was used, the rate would be positive).";
} else {
resultDiv.innerHTML = "The calculated average reaction rate is:
" + reactionRate.toFixed(5) + " mol/L·s (This rate assumes formation of a product).";
}
}
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