Marble and acid: carbon dioxide and the rate of reaction
Make carbon dioxide from marble and dilute hydrochloric acid, and time how long the reaction takes. Change the size of the marble pieces, the strength of the acid and its temperature.
Core concept
Marble (calcium carbonate) reacts with dilute hydrochloric acid to give carbon dioxide: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂; the reaction goes faster with a bigger surface area (powder), a stronger acid and a higher temperature
Topic: Chemical reaction
In the laboratory, carbon dioxide: A gas we breathe out. Plants take it in to make their food. All key words is made by adding dilute hydrochloric acid: A substance that tastes sour, like lemon juice or vinegar. It turns blue litmus red. All key words to marble chips (calcium carbonate): CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. The gas is collected in a gas syringe, or by the upward displacement of air, because it is heavier than air. It turns limewater milky, does not burn and puts out flames, which is why it is used in fire extinguishers. The rate of a reaction is how fast the products form. particle: A tiny piece that matter is made of, far too small to see. All key words must collide to react, so anything that makes collisions more frequent or more energetic speeds it up: a bigger surface area (crushing the marble into powder), a higher concentration (stronger acid) and a higher temperature: How hot or cold something is, measured in degrees Celsius (°C). All key words. In this lab 1 g of marble always gives 240 mL of carbon dioxide; what changes is how long it takes.
What you will learn
- Describe the laboratory preparation, collection and test of carbon dioxide.
- Write the equation for marble reacting with hydrochloric acid.
- Explain how surface area, concentration and temperature change the rate of reaction.
- Calculate an average rate of reaction.
Before you start
- Know that particles move faster when heated.
Materials
- Marble chips and marble powder, dilute hydrochloric acid, limewater
Equipment
- A conical flask with a delivery tube, a gas syringe, a stopwatch, a water bath
Procedure
- Add 1 mol/L acid at 20 °C to marble chips and record.
- Use marble powder instead, and record.
- Use chips with 2 mol/L acid, and record.
- Use chips with 1 mol/L acid at 40 °C, and record.
How this simulation is simplified
- 1 g of marble reacts completely with 50 mL of the acid, giving 240 mL of carbon dioxide.
- Powder reacts 4 times as fast as chips; warming the acid by 20 °C doubles the rate.