Calculate the Reaction Rate in Graph 1

Use this tool to calculate the average reaction rate between two points on a concentration-time graph. Enter the values observed at the two points (Point 1 and Point 2) on your graph.

Point 1 (Start)

Point 2 (End)

Calculated Reaction Rate

Units: mol / (L · s)

---

How to Calculate the Reaction Rate in Graph 1

In chemical kinetics, the reaction rate measures how fast a reactant is consumed or a product is formed. When analyzing a Concentration vs. Time graph (often referred to as Graph 1 in chemistry problems), the reaction rate is fundamentally the slope of the line.

The Mathematical Formula

The average rate of reaction over a specific time interval is calculated using the following formula:

Rate = |(Δ[Concentration]) / (ΔTime)|
Rate = |(C₂ – C₁) / (t₂ – t₁)|

Step-by-Step Instructions

1. Identify Point 1: Look at your graph and find the concentration (y-axis) at the initial time (x-axis).
2. Identify Point 2: Find the concentration at the final time of the interval you are measuring.
3. Determine the Difference: Subtract the initial values from the final values.
4. Divide: Divide the change in concentration by the change in time.
5. Note on Signs: Reaction rates are traditionally expressed as positive values. For reactants, the slope is negative because concentration decreases, but we take the absolute value.

Practical Example

Suppose Graph 1 shows a reactant with an initial concentration of 2.0 mol/L at 0 seconds. After 20 seconds, the concentration drops to 0.8 mol/L.

• ΔConcentration = 0.8 – 2.0 = -1.2 mol/L
• ΔTime = 20 – 0 = 20 s
• Rate = |-1.2 / 20| = 0.06 mol/(L·s)

This means that on average, 0.06 moles of the substance are disappearing from every liter of the solution every second.

function calculateReactionRate() { var t1 = parseFloat(document.getElementById('time1').value); var c1 = parseFloat(document.getElementById('conc1').value); var t2 = parseFloat(document.getElementById('time2').value); var c2 = parseFloat(document.getElementById('conc2').value); var resultDiv = document.getElementById('rateResult'); var valueDiv = document.getElementById('rateValue'); if (isNaN(t1) || isNaN(c1) || isNaN(t2) || isNaN(c2)) { alert("Please fill in all fields with valid numeric values."); return; } if (t2 <= t1) { alert("Final time (t2) must be greater than initial time (t1)."); return; } var deltaC = c2 – c1; var deltaT = t2 – t1; var rate = Math.abs(deltaC / deltaT); // Format to 4 decimal places or scientific notation if very small var displayRate; if (rate 0) { displayRate = rate.toExponential(4); } else { displayRate = rate.toFixed(4); } valueDiv.innerHTML = displayRate + " M/s"; resultDiv.style.display = "block"; resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }