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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 + 2 HCl → CaCl₂ + H₂O + CO₂ (a) A student wante... 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
The figure should include a delivery tube connected to a flask sealed with a bung or cork. The delivery tube should lead to an inverted measuring cylinder or gas syringe submerged in water to accurately measure the volume of gas produced.
Step 2
Explain, in terms of bond breaking and bond making, why some reactions are exothermic.
Answer
Exothermic reactions are characterized by a net release of energy. This occurs when the energy required to break the bonds during the reactants' phase is less than the energy released when new bonds form in the products. In the case of the reaction between calcium carbonate and hydrochloric acid, the breaking of bonds takes in energy, but the formation of new bonds releases energy. Since more energy is released during bond formation than is consumed in bond breaking, the overall process results in heat release.
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 results demonstrate that smaller lumps of calcium carbonate react more vigorously than larger lumps when exposed to the same concentration of hydrochloric acid. This can be attributed to increased surface area. Smaller lumps allow for more particles to collide with acid molecules simultaneously, leading to more frequent successful collisions and thus a higher rate of reaction. Additionally, increasing the concentration of the acid increases the number of acid particles available to collide with the calcium carbonate, further enhancing the reaction rate. Therefore, the reaction is fastest with small lumps in high concentration.