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Chemistry · 6.2 Rate of reaction · Paper 5/6 practical

Rate of Reaction. Time it.

Follow a reaction by the volume of gas produced (gas syringe) or the loss of mass (balance + cotton wool). Change concentration, temperature and surface area and watch the gradient — the rate — change while the final amount stays the same.

0620 Topic 6.2 — Rate of reaction Gas syringe · balance Paper 5/6 — Practical
Setup — set the variables, then press Start and read the value every 10 s.
00:00
Volume 0 cm³

Shortcuts Space start/pause · Enter record · R reset.

Variables

1.00
25
—

Live readouts

Time t
0 s
Volume gas
0 cm³
Rate now
0
Final (theoretical)
—
Rate = gradient of the curve. It is steepest at the start and falls to zero when a reactant runs out.

Readings — every 10 s

Start the reaction and press Record every 10 s.

Volume vs time — gradient = rate

📋 Method (Cambridge practical procedure)
  1. Gas-syringe method: place the solid in a conical flask, add a measured volume of acid, quickly fit the bung with a delivery tube to a gas syringe and start the stopwatch.
  2. Record the volume of gas every 10 s until the reaction stops (volume becomes constant).
  3. Mass-loss method: stand the flask on a balance, plug the neck with cotton wool (lets CO₂ out, keeps acid spray in), add acid and start the timer.
  4. Record the mass every 10 s; the loss in mass equals the mass of gas escaped.
  5. Plot volume (or mass loss) against time. The gradient is the rate; the initial gradient is the initial rate.
  6. To compare conditions, change only one variable at a time and compare the steepness of the curves.
⚠ Sources of error & precautions
  • Gas lost before the bung is in — connect the syringe quickly and start timing the moment the acid is added.
  • Temperature drift — use a water bath to keep the temperature constant; warmer = faster.
  • Same final volume/mass if the acid is in excess — concentration, temperature and surface area change the rate, not the amount of product.
  • Cotton-wool plug in the mass-loss method stops acid spray loss exaggerating the mass change.
  • Read the syringe at eye level; take readings at regular, frequent intervals.
🎯 Syllabus reference (0620)
  • 6.2 Rate of reaction — describe the effect of concentration, particle size/surface area, temperature and catalysts on rate; interpret data from rate experiments; describe collision theory.
  • 12.1 — measurement of time, volume and mass (stop-watch, gas syringe, balance).

Ask the lab assistant