It is important in this core practical to use appropriate apparatus to make and record a range of measurements accurately, including mass, time, temperature and volume. This includes the safe use of apparatus, and monitoring chemical changes.
This outlines one way to carry out the practical. Eye protection must be worn.
To investigate the effect of changing the concentration on the rate of a reaction.
Calcium carbonate reacts with dilute hydrochloric acid:
calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
The volume of carbon dioxide gas produced can be measured using a gas syringe.
Record the results in a table.
|Time (s)||Volume (cm3)|
1. For each concentration of hydrochloric acid, plot a graph to show:
2. For each concentration of acid, calculate the mean rate of reaction until the reaction stops:
3. Describe the effect of increasing the concentration of acid on the mean rate of reaction. Use your graphs and calculations in step 2 to help you.
Describe how you can tell that the reaction is complete.
No more gas is produced, and the line on the graph becomes horizontal.
Evaluate the hazards and the precautions needed to reduce the risk of harm.
|Hazard||Possible harm||Possible precaution|
|Hydrochloric acid||Causes skin and eye irritation||Wear eye protection|
|Fizzing in the reaction mixture||Acidic spray or foam escaping, which may damage skin and eyes||Use a large conical flask so there is plenty of space inside and do not look over the top when adding the calcium carbonate|