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Calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2019 - Paper 1
Question 5
Calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ (a) A student wanted... show full transcript
Worked Solution & Example Answer:Calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2019 - Paper 1
Step 1
Complete Figure 3 to show the apparatus that could be used to measure accurately the volume of gas given off in two minutes.
Answer
To measure the volume of gas given off, a delivery tube should be connected to a flask sealed with a bung or cork. The other end of the delivery tube can be placed under water in a measuring cylinder or gas jar to capture the gas produced. This setup allows the gas to be collected without letting it escape.
Step 2
Explain, in terms of bond breaking and bond making, why some reactions are exothermic.
Answer
Exothermic reactions release heat due to the overall energy change resulting from bond breaking and making. When bonds in reactants are broken, energy is absorbed. However, the formation of new bonds in the products releases energy. If the energy released during bond formation is greater than the energy absorbed during bond breaking, the reaction is exothermic. This is due to the energy differences in the bonds being stronger in the products than in the reactants.
Step 3
Explain, in terms of collision of particles, how these results show the effect of the size of the lumps of calcium carbonate and the effect of the concentration of the acid on the rate of this reaction.
Answer
The rate of reaction is influenced by the surface area of the calcium carbonate and the concentration of the hydrochloric acid. Smaller lumps of calcium carbonate have a larger surface area compared to larger lumps, allowing more frequent collisions with hydrochloric acid particles, which increases the rate of reaction. Additionally, a higher concentration of hydrochloric acid means more acid particles are present in the same volume, leading to a higher frequency of collisions. For example, in the experiments, 5.0 g of small lumps reacted with 0.50 mol dm⁻³ acid produced more gas compared to the large lumps, demonstrating that smaller lumps and higher concentrations yield faster reaction rates.