Investigate how concentration, time, and temperature control the speed of a reaction. Compare zero-, first-, and second-order rate laws and their half-lives, watch temperature raise the collision rate for A + BC → AB + C, and explore how Le Châtelier's principle shifts a system at equilibrium.
Accessibility: This is the accessible version of the lab, built following WCAG 2.1 AA guidelines. It adds screen-reader support, full keyboard navigation, and text descriptions of the interactive diagrams. If you encounter any barrier, please let us know through e2innovations.ai so we can address it.
Theory — Kinetics and Equilibrium
Rate Laws and Reaction Order
The rate of a reaction is how fast a reactant is consumed or a product is formed. The order describes how the rate depends on concentration. Each order has its own integrated rate law and a characteristic straight-line plot.
Integrated Rate Laws (reactant A)
Zero order: [A] = [A]₀ − k t (straight line: [A] vs t)
First order: ln[A] = ln[A]₀ − k t (straight line: ln[A] vs t)
Second order: 1/[A] = 1/[A]₀ + k t (straight line: 1/[A] vs t)
Rate = k[A]ⁿ, where n is the order (0, 1, or 2)
Half-Life
The half-life (t½) is the time for the concentration to fall to half its value. It depends on the order.
Half-Lives
Zero order: t½ = [A]₀ / (2k) (shorter as it proceeds)
First order: t½ = 0.693 / k (constant — independent of [A]₀)
Second order: t½ = 1 / (k[A]₀) (longer as it proceeds)
Only first-order half-life is independent of concentration
Temperature, Collisions, and Rate
Raising the temperature increases both the frequency and the energy of collisions, so more collisions exceed the activation energy. For A + BC → AB + C, the rate of formation of AB is Δ[AB]/Δt, and concentration = number of particles ÷ volume.
Le Châtelier's Principle
If a system at equilibrium is disturbed, it shifts to partly oppose the change. Adding reactant shifts toward products; removing product shifts toward products; raising temperature shifts in the endothermic direction; raising pressure shifts toward the side with fewer gas moles.
Order
How rate depends on concentration (0, 1, 2). Each gives a different straight-line plot.
Half-Life
Time to halve the concentration; only first-order t½ is constant.
Le Châtelier
Equilibrium shifts to oppose a change in concentration, temperature, or pressure.
Order
Integrated law
Linear plot
Half-life
Zero
[A] = [A]₀ − kt
[A] vs t
[A]₀ / 2k
First
ln[A] = ln[A]₀ − kt
ln[A] vs t
0.693 / k
Second
1/[A] = 1/[A]₀ + kt
1/[A] vs t
1 / (k[A]₀)
Apparatus
The equipment a real reaction-kinetics experiment uses. In the simulation these are modelled for you, but the readings correspond to what each instrument would measure.
Stopwatch
Times how long a reaction takes to measure its rate.
Colorimeter
Follows concentration by colour to track the rate.
Beaker
Holds the reacting mixture.
Thermometer
Measures temperature for the rate-versus-temperature study.
Hot plate
Varies temperature to change the rate.
Reagent bottles
Add catalyst or vary concentration of reactants.
Instructions — Running the Virtual Experiment
The simulation has four sections. Complete each one and record your results, with screenshots, in your lab report.
Part 1 — Rate & Order (Rate & Order tab)
1
Open Simulation → Rate & Order. Choose each order (zero, first, second), set [A]₀ and the rate constant k, and observe the concentration-vs-time curve and the chosen linear plot. Record the curve shape and which plot gives a straight line for each order.
2
Read [A] at two times and calculate the rate over that interval. Record [A]₀, k, and the rate for each order.
Part 2 — Half-Life (Half-Life tab)
1
Open Half-Life. For each order, set [A]₀ and k and read the calculated half-life. Record how t½ changes (or stays constant) as the reaction proceeds for each order.
Part 3 — Temperature & Collisions (Temperature tab)
1
Open Temperature. For A + BC → AB → C, set the initial particles of A and BC and the temperature, then Run. Volume = 5 L, so concentration = particles ÷ 5.
2
Record the initial and final particle counts, the concentrations, and the rate of formation of AB (Δ[AB]/Δt). Repeat at a higher temperature and compare the rates.
Part 4 — Le Châtelier's Principle (Le Châtelier tab)
1
Open Le Châtelier. For the equilibrium shown, apply each stress (add/remove a species, change temperature, change pressure) and record the direction the equilibrium shifts and why.
Simulation — Kinetics and Equilibrium
Kinetics & Equilibrium Virtual LabOrder · Half-life · Temperature · Le Châtelier
Reaction order
Rate law
OrderZero
Rate lawk
Linear plot[A] vs t
[A] at t=50.50 M
Zero order: straight [A] vs t line.
Order & conditions
Half-life
OrderZero
Formula[A]₀ / 2k
First t½2.50 s
Second t½5.00 s
For first order, successive half-lives are equal.
A + BC → AB + C
Result (V = 5 L)
[A]₀4.00 M
AB formed—
Δ[AB]— M
Time— s
Rate Δ[AB]/Δt— M/s
Higher temperature → faster rate.
N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g)
Forward reaction is exothermic (ΔH < 0)
reactants
⇌
products
No shift yet
Equilibrium
Apply a stress
Effect
Stress—
Shift—
Apply a stress to see which way the equilibrium shifts.
Team Questions
Question 1. Which reaction order gives a straight line when you plot ln[A] against time? (zero, first, or second)
Question 2. A first-order reaction has k = 0.20 s⁻¹. What is its half-life? (t½ = 0.693/k; type to 2 decimals, in s)
Question 3. For a zero-order reaction with [A]₀ = 1.00 M and k = 0.10 M/s, what is the half-life? (t½ = [A]₀/2k; type in s)
Question 4. Which order has a half-life that does NOT depend on the starting concentration? (zero, first, or second)
Question 5. In A + BC → AB + C, 12 particles of AB form over 150 s in a 5 L container. What is the rate of formation of AB? (rate = Δ[AB]/Δt; type in M/s, e.g. 0.016)
Question 6. For N₂ + 3H₂ ⇌ 2NH₃ (exothermic), which way does the equilibrium shift if you increase the temperature? (left or right)
Question 7 — Challenge. For N₂ + 3H₂ ⇌ 2NH₃, which way does increasing the pressure shift the equilibrium? (left or right — think about moles of gas on each side)
Example Lab Report
Sample report demonstrating the expected format. Include your concentration data, the linear-plot identification for each order, half-life values, the rate calculation, and your Le Châtelier observations, with labelled screenshots.
To compare zero-, first-, and second-order rate laws and their half-lives, to measure how temperature affects the rate of A + BC → AB + C, and to predict equilibrium shifts using Le Châtelier's principle.
Theory
Each reaction order has a distinct integrated rate law and a plot that gives a straight line. Half-life depends on order. Rate increases with temperature because more collisions exceed the activation energy. Le Châtelier's principle predicts the direction of shift when a system at equilibrium is disturbed.
Temperature run (worked example): A + BC → AB + C, V = 5 L, [A]₀ = 20/5 = 4.0 M.
12 particles of AB form over 150 s → Δ[AB] = 12/5 = 2.4 M Rate = Δ[AB]/Δt = 2.4 / 150 = 1.6 × 10⁻² M/s
Le Châtelier (N₂ + 3H₂ ⇌ 2NH₃, exothermic): adding N₂ → shift right; raising T → shift left; raising pressure → shift right (fewer gas moles on the product side).
Analysis
The straight-line test identified the order: only ln[A] vs t was linear for first order. The first-order half-life stayed constant while the zero-order half-life shortened and the second-order half-life lengthened as the reaction proceeded. Increasing the temperature raised the rate of formation of AB, consistent with more frequent and more energetic collisions exceeding the activation energy.
Conclusion
Reaction order determines both the rate-law form and the half-life behaviour, temperature strongly increases reaction rate through collision theory, and Le Châtelier's principle correctly predicts the direction of equilibrium shifts for changes in concentration, temperature, and pressure.
Practice Questions
Show all work. Use the integrated rate laws and half-life formulas, and rate = Δ[AB]/Δt with concentration = particles ÷ volume.
Question 1
A first-order reaction has k = 0.15 s⁻¹. Find its half-life and explain why it does not depend on [A]₀.
Hint: t½ = 0.693/0.15 = 4.62 s; the [A]₀ cancels in the derivation.
Question 2
For a second-order reaction with k = 0.30 M⁻¹s⁻¹ and [A]₀ = 1.0 M, find the half-life. What happens to the next half-life?
Hint: t½ = 1/(k[A]₀) = 3.33 s; the next half-life is longer because [A] is smaller.
Question 3
Given [A] vs t data, how would you decide whether a reaction is zero, first, or second order?
Hint: test which plot is linear — [A], ln[A], or 1/[A] vs t.
Question 4
In A + BC → AB + C (V = 5 L), the number of AB particles rises from 0 to 15 over 120 s. Calculate the rate of formation of AB.
